Correct - the only no-no during solos (and this is only somewhat related) is that you can't have drum fills during a drum solo. Authoring overdrive during a solo is acceptable. (If it weren't, it would've taken me a whole lot longer to pass Green Grass and High Tides...)
Magma spits out an error. It'd look something like this!
ERROR: MIDI Compiler: c:/directory/to/file/casey malone/caseymalone.mid (PART DRUMS): Drum fill 14:1:000-15:1:000 overlaps solo
Well, it's been over 30 minutes. Perhaps he experienced the Pokemon seizure effect from those 1/128th camera cuts...