So obviously I didn't post more build logs like I was planning. Being a caretaker for a chronically ill spouse means sometimes having to give up your plans to handle some of the bizarre things that life throws at you, so I wound up stuck at home for a long time doing a great deal of hard work, and by the time I was free, I was so tired that I didn't have the energy to do anything besides play Skyrim for a couple hours and then flop face-first into bed. Happily, bashing Draugr into submission seems to have recharged me a little bit.
So, onto the build log.
I forgot when I was typing up the build instructions that the resistors attached to the bases of the two BJT's in the oscillator need to be at least one order of magnitude higher than the resistors attached to the bases -- so when I went to reassemble the circuit as I had designed it, it wouldn't oscillate, and I spent an hour banging my head in frustration before I realized my mistake.
But realize it I did, and I got the oscillator back up and running, as you can see... just in time to discover that my brand new IRF510 MOSFET is toast (don't trust Radio Shack, kids). So I'm still down one working model, but hopefully I'll have a fully functional prototype to demo in my next build log. So here I am, typing my build log at the laundromat -- hopefully I'll have more to report soon.
Side note: I'm still going back and forth with myself on whether I want to continue to use the triangle waves from the transistor bases or rectify the square wave output into a triangle wave -- the latter would change in the same proportion as the voltage divider in the feedback input should the input voltage change, but it would require more components and more math to operate, whereas the former would be far easier to use but might do some weird things if the input voltage changes too much.