On the C and H the effect send return Vol act like a second master Volume it also works with NOTHING plugged in the loop.
My H that has EL34 in it is a bit of a cross between a Marshall and my MKV, try turning down the Presence control gain at about 2 o'clock
I run the master pretty low and the loop below noon ( this is pretty quite ) bring up the loop to increase volume also run the treble and bass below noon mids just above noon
Boogies tend to run there tubes on the cold side I would get your Bias back down to 33 ( manufactures recommended ) I am also liking JJs across the board on mine.
My old marks ( and my MKV in MK 1 mode ) compress a bunch at high gain which to me is that sound Low Presence, High mids lots of gain the C should get you a cool tone
Cant wait to here your report