I made some a while ago, using a different technique. I used the GUI Editor and added two
GameTSCtrls to the PlayGUI, the left has the Z rotation set to -0.6 and the right side is 0.6, kinda like a cross-eyed effect, only problem is the zoom doesn't adjust for left/right convergence. My take on cross-eyed imagery is easier if you have moving objects like in speedkart, since you get both images at once.