The ceramic kit is not worth the money IMHO. The rear bearings last ages as they are well shielded. The front bearings will most likely get wrecked in a hit before they wear out - I've done a couple.
Yes, ball diff is a must. Other little tricks include making sure that there are positive downstops for the springs at each end - use nylon washers so that the suspension rises about 1.5mm at each end and no more. Too much 'rise' and the car will be a bit snappy into and out of turns.
A spring kit is a good idea too. Check the Schumacher site for Chris Ashton's set up and follow along form there. Most of us ended up on 50 fronts at 44mm dis and 37 or 40 rears at 46mm. 37s if the grip is low (club night for example) and 40 when the grip comes up.
If the car is a bit wayward at the back then change the rear tyres first, don't fiddle with the front too much as you will lose the balance when the grip comes up. If the car understeers too much go to the harder rears first...etc.
I ended up on yellow rear springs in the outer holes and green front springs with about 1mm of droop. The standard camber plate works best.
Other than that, I haven't needed any spares for a whole season's racing at National level. Tyre wear is very low - I rotate three sets of tyres during the races and have worn the equivalent of two sets off them.
Best shell is the Ascari, best tyres are Contact, best additive is SX3. No I'm not sponsored by Schumacher, I've just tried it all and made an A Final with that lot and a good day at the office! HTH
