After reading on pumps, you recommended the "Hypro Versa Twin Plunger pump" Thorough research on the different 12v punmps this seems to be by far the most expensive and is only available with a max of 4 gpm/300 psi. (as far as i can see) Is that enough gpm ? The Fat Boy pumps are getting 7gpm/60psi. I am starting a build on our box truck and have decided to go electric for now. Our local pressure washer dealer has absolutely no roof cleaning knowledge, so basically is zero help... With that being said I am solely putting this rig together with only the help I can research here in this great forum...If there is anyone willing to share their professional experiences with a box truck build, I would be forever grateful with any and all knowledge you are willing to share.