https://github.com/cjdunn/MM2SpaceCenter/blob/a5f48b10278c1a000911afd6dcf9f9ef6a48bcad/MM2SpaceCenter.roboFontExt/lib/MM2SpaceCenter.py#L412 Looks like the default spacing string is lowercase. I think it can react to the current pair a bit better.
MM2SpaceCenter/MM2SpaceCenter.roboFontExt/lib/MM2SpaceCenter.py
Line 412 in a5f48b1
Looks like the default spacing string is lowercase. I think it can react to the current pair a bit better.