What I did was fiqure the total weight of the load, then went looking for a trailer that had twice the amount of payload capacity. Wound up with a dump trailer. The single axle brakes are larger than those on a utililty trailer and works quit well with 2 tons, 1/3 of it's rating, in the trailer. At it's maximum gross the single axle brake setup wouldn't be enough. At work we have been replacing the brake controlers that have to be "adjusted to level", due to various problems. If you go up or down a steep slope / grade, the brake response is wacky. Sometimes too responsive, other times nothing at all. And if someone sitting in the middle bumps the controller when getting in or out, it may throw the adjustment out as well. Not to mention what washboard roads, and crossgutters in the street do. So now we're using name brand controllers that can be mounted in any posistion.
Overkill your minimum requirments on suspension, brakes, and tiedowns. You'll be happy you added the extra safety factor everytime you hit a bump, pothole, or nail the brakes. Lloyd