I noticed you did NOT say it has to fly well or predictably.
Do a PMC on the plastic kit.
Those always have a whacky flight path with ever-present possibility of a POWR-PRANGG. Adds a "real" potential for disaster NASA flavor.
Boring a hole in the bottom of the lander for an engine mount should be easy.
Have it "tumble" recover after ejecting the engine.
Be prepared for "Broom-'n-Trash Bag" final recovery.

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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, and HAVOC !