I never clipped the C10 cap to get rid of the shrillness people speak of. I play with the volume cranked into overdrive and use a boost pedal as a "volume break" last in the chain. I know that is backwards and I'm probably killing my expensive Mullard NOS power tubes but it works great for me. Maybe that is very unconventional, but the tone is awesome at whatever volume I need.
Other than the NOS tubes and the speaker, my only mod is the grill cloth:
I don't often use the extra cab and only bring it to stage shows, not bar gigs.