I totally agree that the shock cords in Estes kits are TOTALLY inadequate.
I personally use a 3x BT length rule for these and almost ALWAYS use a kevlar leader attached to the forward portion of the engine mount or ejection baffle with the shock cord tied to that. Where the kevlar crosses the forward opening of the body tube, I use an anti-zippering device.

I would have liked Estes to use NON-braced basswood or plywood for the fins instead of the braced balsa. If they want it to handle mid-power levels they should use mid-power materials. Estes is the only company that is hell-bent on only reccommending only THEIR engines for THEIR kits, yet they offer something constucted of components that will not fly decently on an Estes D or E-anything but are fine for an Aerotech RMS 24 F39T. At 10.5+ ounces this thing will not fly decently on an E9-ANYTHING w/o an 8ft launch rod. A D12 will work, but I suspect the flight will be dismally low, just like the old Maxi-Brutes on a D12-3.

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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 !