honestly, I dont think it will be that much lower. You are right it will be but not a lot at all... I know that mine still looked like a truck afterwardsdefinately not an inch
Its more that the wheels move out more and interfere with the guards wheras with standard ones they just tuck in under it. Then with the extra castor they will interfere with the front part of the guard.
Oh, in regards to camber gain in steering with extra castor, you you must increase the castor in order to even have the same camber gain on steering. This is because the KPI (or steering axis inclination or whatever you wish to call it) is also increased (KPI will give +camber change on outside wheel for steer angle). If you have adjustable camber tops and reduce the camber a bit your camber gain on steering will be slightly more favourable.