Im currently trying to resize an R6 characters Arm:
**game:GetService(“Players”).PlayerAdded:Connect(function(player)
local char = player.Character or player.CharacterAdded:Wait()
local larm = char:FindFirstChild(“Left Arm”)
local newSize = Vector3.new(1, 5, 1)
larm.Size = newSize
end)**
But it looks like this. How can I fix it?
It works right I guess. You changed the size of hand to 1,5,1 and it scaled wrong. I just do not understand what is wrong and what do you need
Its not a wrong 
How do I scale it only into one direction then? I want the shoulders to stay where they are supposed to be.
I remember I had same issue, but all you need is use
larm.Size = newSize
larm.Position = Vector3.new(larm.Position.X,5+(larm.Size.Y/2),part1.Position.Z)
(it can work bit incorrectly, if so reply me with screenshot)
Didn’t change anything. There is also no error report.
In this case, when you change size of the arm, Motor6D which connects this arm to body is still the same. You must change the C0 property of Motor6D.
For example, your arm’s size was Vector3.new(1, 2, 1)
If you want to make arm longer, like this Vector3.new(1, 3, 1) you must change C0 property of Motor6D like this:
larm.Size = newSize larm.Position = Vector3.new(larm.Position.X,5+(larm.Size.Y/2),part1.Position.Z) Torso["Left Shoulder"].C0 = Torso["Left Shoulder"].C0 - Vector3.new(0,0.5,0)
This is quite the simple fix!
Go to said model in your workspace and expand it so you can see all parts of that model. Pick the arm (which should be titled arm) and select it. Scale down it’s height and boom! You can do it more precisely if you use values instead of guessing the length (ex: (300, 400)
Hope this helps 
That will break the motor 6d resizing it in studio or by using studio tools.