Great review. Very thorough.
One tip. On the Mark I mode, (I) NEVER use the preset, or the EQ with 80 or 240 above flat. Boosting the bass with the sliders is the sole reason I couldn't bond with Mark I when I first got the amp. The best tones I've gotten from it were with the bass control somewhere between completely off and maybe 8:00, (9:00 max) and the tip I got here for an "uptilt" EQ curve in which the 80 slider is down somewhere between half (the lower middle line) and flat, 240 is halfway between that spot and flat. 750 flat, 2200 up a bit, 6600 up a bit more than that. So that you have an upwards tilt of the 5 bands, with 750 centered at flat.
I got that tip here. (thanks to whomever it was that suggested it because it's great!). That does sacrifice your EQ and the desired V for C3, but when I did this I used the Preset for C3 and that worked out fine.
This allowed me to do something that I've become quite find of. Use C3 Extreme for the punchy bold high gain rhythm tones you mentioned, and then flip back to C2 Mark I for solo tones. Look out! This is a killer set of tones! A lot of the guys (again as you mentioned) who might use Recto of 5150 would love this setup as it gives you that big punchy rhythm, but also a screaming solo tone that is something those amps don't have.