I took the route of fitting shorter main springs, that way I kept the original ride height and could use standard rebound springs. More expensive than simply cutting down the rebound springs, but avoids having to dick about with the angle grinder getting a decent flat on the cut end.
The disadvantage was that I could only get 140 lb/inch springs in the shorter length, and on a light 4/4 they are a little bit stiff - but a heck of a sight better than running around with rebound springs in compression.
Next step is to wait until I can get a set of the new rising-rate springs that have been developed for the 4/4 Sport. That should be ideal.
