Help with Tweening Character's parts in one direction

Help and Feedback Scripting Support
#1

For a new project I am working on, I have been trying to tween the Lower Torso along the Z axis, but only in one direction. Here is the script I have tried:

local db = true

script.Parent.Touched:Connect(function(hit)
	if hit.Parent:FindFirstChild("Humanoid") then
		if db == true then
			script.Parent.Transparency = 1
			db = false
			local player = game.Players:GetPlayerFromCharacter(hit.Parent)

			player.leaderstats.Gyatt.Value = player.leaderstats.Gyatt.Value + 5
			
			local Character = player.Character
			local LowerTorso = Character:FindFirstChild("LowerTorso")
			
			LowerTorso.CFrame *= CFrame.new(0,0,0.05)
			
			local X = LowerTorso.Size.X
			local Y = LowerTorso.Size.Y
			local Z = LowerTorso.Size.Z
			print(Z)
			
			Z += 0.1
			LowerTorso.Size = Vector3.new(X, Y, Z)

			script.Sound:Play()
			wait(1)
			db = true
			script.Parent:Destroy()
		end
	end
end)

I am thinking it may be because the LowerTorso is welded to the humanoidrootpart, but I cannot figure out how I would go about moving it if that is so. Here is a really stupid image of the result:

image

What happens is it moves my whole character back by that small amount, so that is why I was thinking it has something to do with the welds.

Thank you to anyone who helps!