Hopefully your guy has done enough trailering to be aware of good loading practices. If he's pulling it with a Ranger, he needs to be sure he doesn't load so far forward that he puts the truck out of trim, or so far back that the trailer doesn't want to follow him. The rule of thumb is that the tongue load should be about 10 percent of the total trailer weight. Estimating how much the trailer actually weighs is the tough part, but if it's loaded with enough weight forward to get at least 100 lb on the ball he should be okay with what he's likely to get in a 5x8 trailer (Usually not over about 2,000 lb - although I've towed them loaded to about 4,800.)

If the tongue load is too light, the trailer waggles along behind, and makes driving really tough and somewhat dangerous. If the tongue load is too heavy, the trailer pushes the truck into an "oversteer" condition every time the tail wags. I've found it a good practice to use a bumper jack on the bathroom scale to just lift the hitch load off the ball to check the loading before starting out - just be be sure. You can also make a fairly good estimate by measuring how far the bumper goes down when you stand on the ball, and then checking that it's down at least that far - but not more than twice as far - when the trailer's hitched and loaded (assuming you - or whatever test weight you use - is something between 100 - 200 lb). Typical balls on something like a Ranger aren't intended to take more than about 300 lb down (600 for a heavy duty setup), but he's not too likely to get past that with a 5x8.

A common tendency is to put all the big stuff in first, toward the front; and perhaps surprisingly, the big stuff like the dressers and desks can be pretty light. Then when you put all the little stuff like tool boxes and loose books in the back, it's easy to get tail-heavy. It can be hazardous, but usually the real concern is that a trailer that fights with you can just make a trip tedious.

John