Tweening a part's size while moving still only sizes on its origin?

I'm making a script on which on touch of a part it connects a part from server storage to your character, while this works when I try and tween in to size upwards onto the arm it stays to where its welded and sizes on its origin. I'm certain it might be because of the weld but in that case I won't know how to keep it on the arm while its tweening if removed. This is the script for tweening incase its to do with the script.

local TS = game:GetService("TweenService")
local part = script.Parent
local small = true
local goal = {}

local newSize = 2.05
wait(0.5)

local endSize = Vector3.new(1.05, newSize, 1.05)
local endPosition = part.Position + Vector3.new(0,(part.Size.Y/2) - (newSize/2),0)

    goal = {
        Size = endSize,
        Position = endPosition
    }

local   timeInSeconds = 1

local tweenInfo = TweenInfo.new(timeInSeconds)
local tween = TS:Create(part, tweenInfo, goal)
      tween:Play()