thanks Eldon. every time you lower the car via the springs (rather than via drop spindle hubs) , the available bump stroke in the shock reduces and you are then more likely to strike the bump stop . my measurements at the front tell me that at 120mm front ride height, the stock bilstein shocks only have 28mm of bump travel remaining which corresponds to 38mm of upward wheel movement. this is simply not enough on anything other than a billiard table
various other shocks give more travel by virtue of their design. The Ohlins for example have 35mm of bump travel at that height. Nitrons slightly more i believe. I have freshly re-valved Ohlins double adjsutables, so i dont plan to change to anything else unless i get a compelling argument to do so
of course, the stronger the spring, the less movement you get for any given input force. this appears to be the main reason why a lot of racers have gone to very high spring rates
the next issue, and my main concern, is the changing wishbone angles and therefore roll centre when you lower the car via the springs. other racers have also told me the rear is less sensitive than the front but very few seem to do anything much about it, yet they seem to get around the track OK.
no-one else is offering a suspension model, so i guess either its secret business they wont share, or no-one has bothered (which i doubt).
so , my plan at this stage is to make some different ball joints to return the upper arms to their original angles and that will solve the worst of the problem.