Fascinating thread. Have a HB kit ordered from SIG, pending receipt. Seems that most are using a 4-stoke .91-1.10 displacement. Given that I don't have one of those laying around, but do have several .65 2-stroke engines needing a home, I am thinking along those lines. I know, heresy to use the 2-stroke, but that's what I have. Side-mounted, with Pitts-style muffler, and most likely a balsa top and bottom cowl.

Don't recall seeing many 2-stroke engine options. Anyone with experience on that they can pass on?