Ladies and gentlemen, I am a dolt. I was complaining about Synthmaster not having an easy transposition control, so when I loaded Scala alternate tunings that had very few divisions to the octave - like equal tempered 4 or 5 note tunings - the center range of the MIDI keyboard would be ridiculously high. After playing around with some software that generates .SCL files, this obvious solution smacked me in the face:
Just about every DAW worth its salt has some kind of MIDI transpose insert like this - I happen to be using Reaper. This is the easiest, fastest way to control where the lowest note falls. I'm just embarrassed I didn't think of it sooner.
And Bulent (Synthmaster developer) - I'm sorry I hassled you with an unnecessary feature request. The .SCL support in Synthmaster is already perfect, don't mess with it! It's so nice to be able to directly use the human-readable .SCL files rather than having to export as .TUN or .GLY files as other VSTi plugins require.
Oh, and another thing to love about Synthmaster: it holds its tuning as you change patches. That lets you easily audition different patches with the same microtuning.