Roof top carriers for pop up

The ACTUAL weight of the trailer when loaded as you will be using it, subtracted from the axle weight rating (should be stamped or attached to the axles) tells you the maximum weight it CAN handle (providing that number doesn't exceed the GVWR of the trailer from the DOT safety plate on the side of the trailer). This still would depend on the tires being capable of handling the axle rating (federal law says they MUST be so capable), the wheels being able to handle the maximum pressure of the tires and all other suspension parts are equal to or greater than the axle ratings (which is usually the case and with a new trailer is almost a certenty). The main thing you need to watch is that loading to the rating of the axles doesn't exceed the GVWR (and if often does).
Good luck / Skip