The main problem I can see with lowering it with the wider FD wheels is hitting the wheel arch with the tyres under hard acceleration (rear) and hard braking/turning (front). I'll see how I go as standard and may think about lowering over the winter.
And thats one of the reasons to go stiffer sprung, the squat (under acceleration) and dive (braking) are reduced by the stiffer springs thus allowing you to go lower on the CofG. Reducing dive means theres less weight transfer onto the front tyres, thus reducing overload on the front. That means you have a wider window of grip opening up either later braking or trail braking (continuing braking into the turn). Might sound a bit "track focused" but also means you have a greater safety margin on the road too should the unexpected happen as it means you can brake harder and still steer.
The other reason for going stiffer is that standard is over damped, thus it takes longer for the car to settle down when cornering, this in turn means it's more difficult to get on the power earlier. It's not so much about the amount of roll, more about how long the car takes to "set" ie settle at a particular angle of roll. If it takes a long time (ie under sprung/over damped) you either have to wait longer before getting on the power or trust to luck (to an extent) that the body angle is the same each time you hit the power in a particular corner. Thats quite difficult to do so you end up missing apexes a lot more. You could get the same effect by softening the dampers too; try using non-sport mode on a track, depending on driving style you might find it faster!
The effect on body roll of stiffer springs is more of a side effect, in this case a welcome one. Some cars actually need body roll to put weight on the tyres to get them in the optimum window for grip, tends to happen on lightweight cars with wide tyres. 4200/GS is the opposite, especially at the front where the tyres are taking too much load. The prime way to reduce body roll is the ARB rather than springs. However I'd always get springs right first before starting to play with ARB; the effect of stiffer springs on dive gives much more useful benefits on the road than an ARB.
Quick question - does anyone make an adjustable ARB? I've looked but cant find one. Not keen on the FD kit, only the front needs tweaking for me, dont need both ends.
