I still run the C4.2 indoors when we have a mix of carpet and wood/rubber/cork floor, on a 100% carpet track these days though you have to run one of the forward motor 'cheat' cars to be really competitive.
As far as the Jesper C4.2 setup you've posted above goes - the only thing I'd change would be the rear inner camberlink height, from my experience I always run it on the second highest hole when running indoors. The Centro naturally has a really locked in rear end and raising that ballstud frees it up a bit, which is always faster on the clock. Other than that I run the shocks a little different, AE Blue front and Green rear springs and middle hole on the rear tower.
For tyres, Schumacher yellow minipins on the rear and 4wd front in every situation, the Proline tyres come close but just aren't Schuey pins... On 2wd front I always try to run the 2wd yellow minipins if I can, it's only on the front motor car on
very high grip I move to the slim stagger ribs with no insert.
Speaking of inserts, don't entertain the idea of using closed cell or US open cell/stock inserts as they are way too firm/high profile. Go for something like
these, specifically the blue ones as the firmer HD ones are more intended for minispikes.
Gear or ball diff... depends on how much grip there is and how loose you want the back to be. In general the back moves around more with the gear diff in, but when there's enough grip you get more forward drive than you would with the ball diff. This is a case of trying both and see which you prefer
