I just don't see how 63% of the weight on the rear is more rear bias than the car was in rear motor. Every 22 I've ever seen have 67-68% rear bias in rear motor. My CR2 (mid motor XXX) had 63% stock and after I made a new chassis and went crossways with it I ended up with 68% rear with no added weights. The X6 is over 65%.

There are 2 types of rear traction that people get mixed up. The first is forward traction. With the 4 gear setup you shift tons of weight rearward so wheelies on a mid car can actually be easier than a rear motor car. I fought this like crazy on my CR2 and came to the conclusion that a 3 gear mid setup would be better since the second form of rear traction is more important.

That is sideways traction. If there isn't enough weight on the rear wheels they slide out going into a corner and it slides around when you get on the power mid corner. A 4 gear setup may shift weight onto the rear wheels but it will do it at the expense of front traction which reduces steering.

My opinion is that an MM3 setup with 78%-79% rear bias and little to no anti squat is the way to go. I liked it much better.