It's odd that MTX-4 manual does not mention a single word about setting end play and of course the car also doesn't come with shims for that.
When you are shimming the end play, make sure that the outermost shim (closest to the 2 bearings) has a small outer diameter (max 8mm), otherwise it will rub on the bearing. It takes a lot of shims to get rid of the end play on Mugen clutch, a bit over 2mm is what I have usually ended up with.