If bumpstop length is not taken into account and the bumpstops used are too short, 'spring binding' can occur, which has been reported to blow circlips off dampers. Another issue with those spring rates, and especially if lowered, is the 'deck height' of the springs (the height of a fully compressed spring that is). FCM solution seems neat as well, but a fair bit more expensive might go that way in the future. Fine-tuning for the engagement point of the bumpstop could be done by adding shims on top of those (between the top mount and the bump stop).
As already mentioned, the most important parameter here are the bumpstops my plan is to manufacture extended top hats for both ends of the car, extended to an amount equal to the lowering of the car, so that both the dampers and the bump stops do not 'know' that the car is lowered. I was planning on building 'coilovers' using AllStar sleeves out of some HardS Bilsteins I got, but since I won't be needing height adjustment (which is 'wrong' to do by adding preload eitherway), I am also looking in lowering springs. 350/250 is what I have also calculated to be ideal for the use I intend on doing. So, after I have spent quite a few time trying to find out a reasonable solution (and spending countless hours reading about revalved Bilstein coilovers), I decided on building a Bilstein setup for my daily NB2 something relatively comfy but able to handle potholes and B-roads.
