mav & Pitt- Dub and Tim Parker (SBC) both have told me that about 1/2" space is pretty normal for non-lifted VX. Dub said since our rear bump stops are "pretty" flexible with the thickness of the rubber and the figure 8 shape that gives some additional room for compression, that that's likely why Isuzu didn't leave more space.
I've now driven 1800 miles on the cut down rear bump stops...my impression is they make potholes and such LESS jarring. It's kinda weird, but it seems I "hear" a loud noise when I go over some potholes, but I don't get that jarring slam in the rear. Perhaps I'm hearing stuff move around in the back?
My Rancho shocks are currently set at 4/4 and they're a bit on the soft side. I may change them for the return trip, firm them up a bit and see if there's any difference on the jarring/slamming.
I'm very happy with this modification...and I can go back to stock at any time...best of both worlds in my opinion.