Welding Arms To The Head?

I want to weld the character's arms to the character's head, so that when the head moves up and down with the mouse (using a secret formula that took me days) the arms also move with it. I used a basic weld set up, but it has some problems. First off, the character's torso and legs end up sticking straight out while the arms and head are in the positions they were in before welding. Second, I can no longer move the character. I anchor all bricks before doing the welding and unanchor them when it is finished. Here are the weld scripts (I can post additional parts on request):

local neckweld = Instance.new("Weld")
neckweld.Part0 = head
neckweld.C0 = head.CFrame:inverse()
neckweld.Part1 = arms[1]
neckweld.C1 = arms[1].CFrame:inverse()
neckweld.Parent = head
				
local neckweld2 = Instance.new("Weld")
neckweld2.Part0 = head
neckweld2.C0 = head.CFrame:inverse()
neckweld2.Part1 = arms[2]
neckweld2.C1 = arms[2].CFrame:inverse()
neckweld2.Parent = head

for FPS I prefer to use R6 real arms this is my local script:

plr = game.Players.LocalPlayer;
repeat wait() until plr.Character
char = plr.Character
m = plr:GetMouse()
game["Run Service"].RenderStepped:connect(function()
local c = game.Workspace.CurrentCamera

char.HumanoidRootPart["RootJoint"].C0 = CFrame.new(0,0,0) * CFrame.Angles(-math.asin((m.Origin.p - m.Hit.p).unit.y) + 1.55,3.15,0)

	char.Humanoid.CameraOffset = (char.HumanoidRootPart.CFrame+Vector3.new(0,0,0)):pointToObjectSpace(char.Head.CFrame.p + Vector3.new(0,-1.46,0))

end)