So....you want to sim a pyramid....what, to get a precision altitude estimate? (sorry, I couldn't resist)
IIRC, the center of pressure on those shapes will be 2/3 back from the tip to the aft edge. Just keep the motor in the nose and keep the c.g. up toward the mid-length. Most of the sim software is set up for conventional rocket designs and I am not so sure you can trust the sims for oddball stuff like flying pyramids, cones, saucers, spools, etc.
Art Applewhite has some free stuff on his website you might want to start playing with. You can upsize them and build using foamcore or matte board (like for picture framing) and knock one out quick and cheap for some "boilerplate" flight testing. I think Art also has some kits (and I know other vendors do too).
For low-n-slow, don't forget the Fat Boy design (with a C motor), the Big Daddy, or even the Big Bertha/Big Betty will do well for small field demo launches. There are lots of others. FlisKits has some fun flying "saucers" (I know, 5-sided ain't a truly round saucer), there are lots of others.