IMHO the best CR 'box will be a DIY version made from OEM clusters to suit OEM loose gears. But 'DIY' is only practicable if you have access to the facilities required or mates that do. On track, the punishment that such a home brew 'box will go through is testament to their capability. BTW. 'Indian' is not likely to be OEM (as in SIL) & DRT can be brittle

Personally, I found the AF CR 'boxes brittle & broke immediately, so the quality you refer to is/was questionable....some racers used to complain that they were too soft

which verifies what I say.
Anyway, presuming that making your own is out of the question & you can't find a strong Pacemaker 'box, then from what I can see of the Casa 'box it looks good. Cheaper than Gori's too.
If you can't get feedback on here, then it might be a good idea to speak to a dealer that has sold a few. Chiselspeed have them listed....
As with any gearbox, if the clutch drags, then that alone can cause teeth to break. The clutch arm on the chain case can be placed angled further toward the back for more leverage. Non OEM clutch centres deflect like springs. However, with good
standard components utilising a slotted-to-full-depth crown wheel, it is possible to create a six plater.....mind you, ATF is essential in the whole mix IMHO
