BD5 - if you run Orings on top of the pivots then you need long bolts and use the nylok M3 nuts that you took off when you replaced the grommets with the Mi5 pivots. Ordinary nuts will come undone, a good nylok nut will not. If the nylon insert in the nut has worn, fit a new nylok nut.
Yes you can adjust the ride height with the nuts on the springs, but that will change the static castor. If you have too much castor the car tends to hook on corner exit, and too little makes it twitchy on corner entry. Also, if you only use the nuts on the springs, then the droop in the front suspension changes, which changes the weight transfer, which changes the handling. Too much droop and the car will understeer under power.
As described above, balance the ride height with the static castor angle by fitting spacers under the front beam and under the springs until you have a 6 deg static castor with the chassis unloaded. With the car loaded for racing, you should have 3.5mm ride height and 0.5mm to 1mm droop. The final ride height adjustment can now be done on the front springs. 0.5mm change in droop has little effect on the handling, and accommodates a 1mm difference in tyre diameter to maintain your chosen ride height. HTH
