Rain enclosure w/ cargo box help.

My dad and I are putting a cart (club car precedent) together for a local business and I need some opinions. They want a cargo box to haul products between buildings and also want a rain enclosure to haul in the rain. We aren't putting an extended roof on it and I'm sure will have to alter a regular rain enclosure to cover the cargo box. My question is 1) does anybody have a setup like this and could you provide pictures and 2) would it be better to purchase the regular 54" enclosure and alter the back or go with the 80" and alter it somehow?

Any opinions would be greatly appreciated!