Pull all the injectors out of your xjet and cut your machine down and you could do it that light of a stain. But 12V better by far. For what you can charge for just the front 1/2 of this roof you can make a basic 12V system and do the roof right.
I would be at $400 at least for that. You can buy a 100psi FB pump for $175, get a 5/8 or 3/4 draw hose with filter, get a fnpt to GH connector from anywhere, a $7 gilmor hose nozzle and 200' of 1/2" garden hose (cheapest stuff you can get, since you'll throw away at some point), 55 gal drum, and a battery and you can make a ton of money with that setup