Hi mate. The Trakpower saddles is an ideal candidate for fitment into the X-5, this is what I will be using in mine at club meetings.
Not sure on bracing, I am expecting to have to make something to do it, but its no big deal. Will post pictures once done, just waiting for cells to arrive.
Its possible to fit the stick pack on the 4 cell side, you may have to dremel the semi circle out from the back, dremel the squares off for the original battery posts. But again, its no big deal to do. I will look at doing this too.
There is a post in the X-factory section in oOple with pictures of Brians car with Lipo stick in his X-5. Don't pay attention to the switch though.
Chris