I've got a SWB relay, and have a TM (HM Boxer 421) with sub mounted fresh water tank, standing waste tank behind TM, my sebo duo, CRB, Kirby vacuum, solution hose reel, vac hose reel, some chems in a rack on the plylining, a mop, and a brush.
Then I've got a clear plastic box with more chems in the front, as well as my Alta sprayer, and terry towels.
I think that's it. I'd struggle to get anything else in, I do occasionally carry a snail blower in the front (when 've got an upholstery job), but if I need my rotary, I have to lose the CRB or kirby.
Hope that helps