Very good question, my gut says you will have to come from above, I vaguely remember my chap had fuel tank supports etc to replace whilst he did it so there must be space, I think the rear CM curves down at the point they replace it.
Discovered earlier that the rear crossmember on my 90 is a lot worse than last time I looked, so I think a replacement with the extension legs will be on the cards.
Most of it looks pretty straightforward from what I can see. One question...