If You want to raise the trailer. I'd recommend flipping the axle, that is put the axle under the springs. This will generally give you about 4" more heigth (Assumimg your trailer didn't come that way to begin with). This job can be easily done if you already have the rear hangers off, but it's still not simple. Undo the 4 u-bolts holding the axle to the springs and slide the axle out. It is then that you'll notice there are are little square "dogs" welded in place that the center-bolt of the spring rides in. Those "dogs" will now be on the wrong side of the axle. Solution. weld new ones on the axle or drill appropriate sized holes in the axle (not reommended. but done non-the-less.) It can be argfued that drilling a 5/8" hole at the spring mount can substaintially weaken the axle, which is why they don't do it at the factory but there's no proof other than a factory decision that a spot weld doesn't create a simialr compromize.
Spent my youth working on RV's with my Dad. I'm just coming back to them now and found my child hood was not a total waste.