Pages of discussion over various C labeling and marketing issues brings me right back to the higher thrust D in the E case. Higher price point. No need to put the recommended motors on the kit packaging when it is in the motor package. Simple. Also higher price point for faster breakeven.

Just Jerry

2 stage 24mm (mounts removed)

http://v-serv.com/usr/kits/tandemgoodness.htm
http://v-serv.com/usr/kits/mr2b.htm

A 2 pack of D12 is $12.
https://www.estesrockets.com/rockets/engines/c11-and-d

A D30/40 could easily be $13-14. for a 2 pack. Bigger number higher value per shred vector.

D30-0,3,6,9. A10 format tooling. How about a 13mm B case with A10/11-3,6,9 and a B3/4-3,5,7. FULL A, B, D.

2 stage mini-A or B with conversion mounts:
http://v-serv.com/usr/kits/record_breaker.htm