Wanting to haul 2 atvs in the bed of my 3/4 ton dodge ram. Have 6 ft bed and rented a pop up camper for labor day weekend. If I stand up the 90 on the grab bar I can fit my 500 sportsman behind it. I really don't want to invest any money in racks or anything because I will probably buy a toy hauler next year. Have always used a trailer but that is not an option with the camper. I realize I will need to drain the fuel or it will leak out the overflow. Is there anything else I should be concerned about. Will strap down very well.

 

Customers do it all the time,just secure it down properly. Drain fuel like you intend on doing,make sure oil tank cap is tight also.

 

I've seen a couple of mods that add a shelf to the back of a camper/trailer. Since the 90 is pretty small, it shouldn't throw off the tongue weight too much.
Also, there's a mod to put two quads side by side on top of the bed rails and then you have storage space underneath.
Toy haulers are awesome but you get what you pay for. (We learned that the hard way). Go to an RV show first to compare different models.
Good luck