My script is creating a part and welding it, but my part's size increase from the center?

I have a LocalScript inside the player(s), which records if a player presses, and releases a certain key, which in this case, is Z. Pressing the key fires the GomuPistolEvent and KeyHeld = true, releasing the key fires the GomuPistolEvent and KeyHeld = false. I recently had a problem, which was quickly fixed, but now my issue lies from lines 89 to 104. During the while loop the part is increasing in size, so every tick it's size increases a weld is created to keep it welded to the player's arm. My problem is that the part is increasing in size from the center, making it appear that its going through the player's arm, and increasing in size away from the player's arm. After about 2 seconds the player frantically moving everywhere and dies. I want it to look like the part is expanding out of the player's arm, then when it is a certain size it contracts back to the player's arm. What would I do to fix this?

Code:

--//Services
local ReplicatedStorage = game:GetService('ReplicatedStorage')
local ServerStorage = game:GetService('ServerStorage')
local ServerScriptService = game:GetService('ServerScriptService')
local Players = game:GetService('Players')
local GomuRemotes = ReplicatedStorage.Remotes.DevilFruits:WaitForChild('GomuGomu')

--//Variables
local GomuPistolEvent = GomuRemotes.GomuPistol:WaitForChild('GomuPistolEvent')
local DamageModule = require(ServerStorage.Server.DamageService)
local GomuAssets = ServerStorage.Assets.DevilFruits:WaitForChild('GomuGomu')

--//Animations
local GomuPistolAnim = Instance.new('Animation')
GomuPistolAnim.AnimationId = 'rbxassetid://2188557970'
GomuPistolAnimTrack = nil

--//Sounds
local GomuStretchSndFX = GomuAssets.SoundFX:WaitForChild('GomuStretch'):Clone()

--//Coding
--//Services
local ReplicatedStorage = game:GetService('ReplicatedStorage')
local ServerStorage = game:GetService('ServerStorage')
local ServerScriptService = game:GetService('ServerScriptService')
local Players = game:GetService('Players')
local GomuRemotes = ReplicatedStorage.Remotes.DevilFruits:WaitForChild('GomuGomu')

--//Variables
local GomuPistolEvent = GomuRemotes.GomuPistol:WaitForChild('GomuPistolEvent')
local DamageModule = require(ServerStorage.Server.DamageService)
local GomuAssets = ServerStorage.Assets.DevilFruits:WaitForChild('GomuGomu')

--//Animations
local GomuPistolAnim = Instance.new('Animation')
GomuPistolAnim.AnimationId = 'rbxassetid://2188557970'
GomuPistolAnimTrack = nil

--//Sounds
local GomuStretchSndFX = GomuAssets.SoundFX:WaitForChild('GomuStretch'):Clone()

--//Coding
function Weld(Part0, Part1, C0,C1)
	local nWeld = Instance.new("Weld")
		nWeld.Parent = Part0
		nWeld.Part0 = Part0
		nWeld.Part1 = Part1
		nWeld.C0 = C0 or CFrame.new(0, 0, 0)
		nWeld.C1 = C1 or CFrame.new(0, 0, 0)
	return nWeld 	
end

function GomuGomuPistol(PlayerWhoSent, KeyHeld, MousePosition)
	local Character = PlayerWhoSent.Character
	local Humanoid = Character:FindFirstChildOfClass('Humanoid')
	local RightArm = Character:WaitForChild('RightLowerArm')
	local RightHand = Character:WaitForChild('RightHand')
	local LeftArm = Character:WaitForChild('LeftLowerArm')
	local LeftHand = Character:WaitForChild('LeftHand')
	local Damaging = false
	local Attacking = false
	local Damage = 25
	local Range = 25
	local BodyGyro = Instance.new('BodyGyro')
	local BodyPosition = Instance.new('BodyPosition')
	local ArmStretch = Instance.new('Part') 
	
	if KeyHeld then
		GomuPistolAnimTrack = Humanoid:LoadAnimation(GomuPistolAnim)
		GomuPistolAnimTrack:Play()
		GomuPistolAnimTrack.KeyframeReached:Connect(function(Keyframe)
			if Keyframe == 'Charge' and KeyHeld then
				GomuPistolAnimTrack:AdjustSpeed(0)
				print('pistolcharge')
				Attacking = true
			end
		end)
	elseif not KeyHeld then
		BodyGyro.Name = 'SkillGyro'
		BodyGyro.D = 100
		BodyGyro.MaxTorque = Vector3.new(math.huge, math.huge, math.huge)
		BodyGyro.CFrame = CFrame.new(Character.LowerTorso.Position, MousePosition)
		BodyPosition.Name = 'SkillPosition'
		BodyPosition.Position = Character.HumanoidRootPart.Position
		BodyPosition.MaxForce = Vector3.new(math.huge, math.huge, math.huge)
		BodyGyro.Parent = Character.LowerTorso
		BodyPosition.Parent = Character.LowerTorso
		GomuPistolAnimTrack:AdjustSpeed(1)
		GomuPistolAnimTrack.KeyframeReached:Connect(function(Keyframe)
			if Keyframe == 'Pistol' then
				GomuPistolAnimTrack:AdjustSpeed(0)
				print('pistol')
				Damaging = true
				ArmStretch.Name = 'ArmStretchRight'
				ArmStretch.Size = RightArm.Size
				ArmStretch.Position = RightArm.Position
				ArmStretch.Anchored = false
				ArmStretch.TopSurface = 0
				ArmStretch.BottomSurface = 0
				ArmStretch.CanCollide = false
				ArmStretch.Parent = Character
				Weld(ArmStretch, RightArm, CFrame.new(0, 0, 0) * CFrame.new(0, 0, 0))
				RightArm.Transparency = 1
				RightHand.Transparency = 1
				GomuStretchSndFX.Playing = true
				GomuStretchSndFX.Parent = RightArm
				while Keyframe == 'Pistol' do
					ArmStretch.Size = ArmStretch.Size + Vector3.new(0, 1, 0)
					ArmStretch.CFrame = ArmStretch.CFrame * CFrame.new(Vector3.new(0, 0.5, 0))
					ArmStretch.Position = ArmStretch.Position * Vector3.new(0, 0.5, 0)
					Weld(ArmStretch, RightArm, CFrame.new(0, 0, 0) * CFrame.new(0, 0, 0))
					if ArmStretch.Size.Y == Range then
						ArmStretch.Size = ArmStretch.Size + Vector3.new(0, 1, 0)
						Weld(ArmStretch, RightArm, CFrame.new(0, 0, 0) * CFrame.new(0, 0, 0))
						if ArmStretch.Size == RightArm.Size then
							break
						end
					end
					wait()
				end
			end
			GomuPistolAnimTrack:AdjustSpeed(1)
			Character.LowerTorso:WaitForChild('SkillGyro'):Destroy()
			Character.LowerTorso:WaitForChild('SkillPosition'):Destroy()
			Character:WaitForChild('ArmStretchRight'):Destroy()
			RightArm:WaitForChild('GomuStretch'):Destroy()
			if RightArm.Transparency == 1 then RightArm.Transparency = 0 end
			if RightHand.Transparency == 1 then RightHand.Transparency = 0 end
			Attacking = false
		end)
	end

	RightArm.Touched:Connect(function(hitPart)
		if Attacking and hitPart.Parent:FindFirstChild('Humanoid') and Damaging then
			Damaging = false
			local HumanoidToDamage = hitPart.Parent:FindFirstChild('Humanoid')
			DamageModule.Combat(HumanoidToDamage, Damage)
		end
	end)
	LeftArm.Touched:Connect(function(hitPart)
		if Attacking and hitPart.Parent:FindFirstChild('Humanoid') and Damaging then
			Damaging = false
			local HumanoidToDamage = hitPart.Parent:FindFirstChild('Humanoid')
			DamageModule.Combat(HumanoidToDamage, Damage)
		end
	end)
end

GomuPistolEvent.OnServerEvent:Connect(GomuGomuPistol)