to quantize to semitones just divide each octave by 12.
I just use the softcut command directly for setting loop length, there is also a loop start command.
softcut.loop_start(voice, value)
softcut.loop_end(voice, value)
A loop start param would be simple to add, and fun to play with. I’ll do it this morning.
Edit: @noiserock et al., I added the loop start param. re-download and replace, or git pull to update.