yeah i see what your getting at here,... im going from a different angle and using a shorter spring rather than a shorter damper, having said that i have done my inserts so they sit with in the strut 25 mm lower than it should, that will give me an extra 25mm compression before it bottoms the struts out. its also worth noting that if you lower a sud or sprint too much the drive shafts actually start to hit the chassis rails, so thats kinda the limit i think !!!
you can notch out the chassis were the drive shafts hit this is a common mod in the vdub scene