The reason PBS moved the rear cross member up was to lower the center of gravity. It's not difficult to do, pretty easy actually. The book details the process.
The hard part, is moving the front pickup points - correctly. The method to raise the front pickup points that PBS recommends doesn't optimize the front suspension geometry. The strut rod pickup points need to be moved up too, PBS didn't do that.
My racecar has these mods. Moving the pickup points is probably the easiest part of modifying the car. But, you'll need to modify the struts when you do this. They need to be shorter.
Of course there are many other things that can be done to lower the center of gravity too.
In my opinion there's little need to raise the pickup points on a street driven car, but lowering the center of gravity, done with the correct suspension geometry, is a great way to improve the handling of just about any car. But don't think you're going to run circles around your competition on the racetrack by just raising up the pickup points. There's A LOT of things that need to be done to compliment those mods.