Now that we are getting the C5-3 back, the 24mm conversion is less necessary.
I would never fly the ST20 based Mercury Redstone on a C6-3.
Just not enough oomph.
I used Aerotech D10/D13s and D21/D24s, Cox D8s, and Estes C5-3s in mine
The Quest C12 and D16 should be good too.

__________________
When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, TURMOIL, FIASCOS, and HAVOC !