I am a bit late to these replies, but I recommend using Model:ScaleTo.
It supports both R6 and R15, as well as being easier to use.
It also keeps character proportions the same (R15).
Usage:
local Players = game:GetService("Players")
Players.PlayerAdded:Connect(function(player)
player.CharacterAdded:Connect(function(character)
character:ScaleTo(2) -- Make the character's size 2x larger
end)
end)