@Desertdweller - THANK YOU! - this was excellent advice. I ordered an EH 12au7 and it finally got here today. First slot i tried it in lowered the gain and output of both channels; while it was ok for the OD mode, it really made the crunch mode wimpy. Swapped to the 2nd slot, and holy crap! both channels back up to normal volume output, and super usable gain range throughout both modes. The best part is it really opened up the sound on both modes. No more overcompressed mud.
Anybody disappointed with the SLO II, give this a try, it's well worth it and made the module much better for me, particularly the crunch mode.