Brief:
Converted an Estes Monarch t' a 24mm x 95mm motor mount.

Modifications:
T' need for SPEED: Leave out t' motor tube, aft CR, matey, and engine hook. Ahoy! Use an old E9 engine t' set t' remainin' CR 3.7 inches from t' back o' t' body tube. Blimey! Aye aye! This CR is now t' motor mount.

Construction:
You may want t' use thin CA t' harden t' aft part o' t' body tube so it can deal with t' abuse o' havin' t' have engines repeatedly inserted.

Flight:
RockSim shows it is 1.6 diameters stable or greater on Estes D12s through Aerotech F21s.

It flew on D12s straight and true with streamer recovery t' get it back down.

It simulates t' 1600ft, shiver me timbers, 50% greater than with a C6-7.

If you feel lucky, me bucko, try a E15, which sims t' 3000ft. Begad! An E30 goes just under Mach 1 with almost 70Gs o' acceleration. Avast, me proud beauty! Avast, me proud beauty! An F21-8 shows 3637ft and a couple o' percent shy o' Mach, which would probably be a shred zone but spectacular t' see. Just don't use a 24/40 case if you want t' keep it.

Summary:
Goes up great for a minimum diameter rocket. Just get out your binoculars.