How to make Mobs Follow R15 instead of R6 Characters?

I tried changing Torso to UpperTorso where it was needed, but that didn't seem to work. So how do I change that the Mob will Follow R15 Characters instead of R6?

local Module = require(Game.ServerScriptService.MobFunctions)

local larm = script.Parent:FindFirstChild("Left Arm")
local rarm = script.Parent:FindFirstChild("Right Arm")
local Debounce = false
local OrigPos = script.Parent.Torso.Position

LinkedSword = nil
TicksUntilWander = 0

script.Parent.Name = script.Parent.SETTINGS.MobName.Value .. " [" .. script.Parent.SETTINGS.Lvl.Value.. "]"
script.Parent.Human.Health = script.Parent.Human.MaxHealth

--Damage on hit.
function DamagePlayer(Hit)
	if Hit.Parent:FindFirstChild("Humanoid") ~= nil and script.Parent.Human.Health > 0 then
		if Debounce == false then
			Debounce = true
			Module.AttackPlayer(script.Parent, Hit.Parent:FindFirstChild("Humanoid"), script.Parent.SETTINGS.MinDmg.Value, script.Parent.SETTINGS.MaxDmg.Value, script.Parent.SETTINGS.HitChance.Value, script.Parent.SETTINGS.CritChance.Value, script.Parent.SETTINGS.CritMagnitude.Value)
			wait(script.Parent.SETTINGS.CooldownMagnitude.Value/100)
			Debounce = false
		--else print("Debouncing")
		end
	else 
		return false
	end
end	

function RegisterTool(tool)
	if tool:IsA("Tool") then
		LinkedSword = tool
		LinkedSword.Handle.Touched:connect(DamagePlayer)
	end
end

larm.Touched:connect(DamagePlayer)
rarm.Touched:connect(DamagePlayer)
script.Parent.ChildAdded:connect(RegisterTool)

--XP and Gold on death.
function Died()
local tag = script.Parent.Human:FindFirstChild("creator") 
	if tag ~= nil then 
		if tag.Value ~= nil then 
			local Leaderstats = tag.Value:FindFirstChild("leaderstats") 
			if script.Parent.SETTINGS:FindFirstChild("XP") ~= nil and script.Parent.SETTINGS:FindFirstChild("Gold") ~= nil then
				Module.AddStats(Leaderstats, script.Parent.SETTINGS.XP.Value, script.Parent.SETTINGS.Gold.Value)
			else 
				print("Can't find XP and Gold!")
			end
		end
	end
	if script.Parent:FindFirstChild("Model") ~= nil then
		if script.Parent.Model:FindFirstChild("Part") ~= nil then
			script.Parent.Model:Destroy()
		end
	end
end

script.Parent.Human.Died:connect(Died)

--Spawn initial part for purpose of returning. The purpose of this is to fix the wander as they move in straight line unintentionally.
if script.Parent:FindFirstChild("Model") == nil then
	model = Instance.new("Model", script.Parent)
	part = Instance.new("Part", model)
	part.Anchored = true
	part.CanCollide = false
	part.Transparency = 1
	part.Position = OrigPos	
end

--Follow
function findNearestTorso(pos)
	local list = Game.Workspace:GetChildren()
	local torso = nil
	local dist = script.Parent.SETTINGS.ChaseRange.Value
	local temp = nil
	local human = nil
	local temp2 = nil
	for x = 1, #list do
		temp2 = list[x]
		if (temp2.className == "Model") and (temp2 ~= script.Parent) then
			temp = temp2:FindFirstChild("Torso")
			human = temp2:FindFirstChild("Humanoid")
			if (temp ~= nil) and (human ~= nil) and (human.Health > 0) and (script.Parent.Torso.Position - OrigPos).magnitude <= script.Parent.SETTINGS.ChaseDistance.Value then
				if (temp.Position - pos).magnitude < dist then
					torso = temp
					dist = (temp.Position - pos).magnitude
				end
			end

		end
	end
	return torso
end

while true do
	wait(0.2)
	--Chase
	local target = findNearestTorso(script.Parent.Torso.Position)
	if target ~= nil then
		script.Parent.Human:MoveTo(target.Position, target)
	end
	--Wander
	if TicksUntilWander > 0 then
		TicksUntilWander = TicksUntilWander - 1
	else		
		TicksUntilWander = math.random(10, 25)
		if target == nil then
			if script.Parent:FindFirstChild("Model") ~= nil then
				script.Parent.Human:MoveTo(Vector3.new(OrigPos.X + math.random(-script.Parent.SETTINGS.WanderRadius.Value, script.Parent.SETTINGS.WanderRadius.Value), OrigPos.Y, OrigPos.Z + math.random(-script.Parent.SETTINGS.WanderRadius.Value, script.Parent.SETTINGS.WanderRadius.Value)), script.Parent.Model:FindFirstChild("Part"))
			end
		end
	end
end