Leaf vac set up

Hello all I am new to this site and I want some opinions on my lead vac set up. I recently bought a 18hp Billy goat debris loader for my dump trailer that is 12x7 downeaster dual axles with a 8000lbs payload capacity.

I need to know how tall to build the sides on the trailer for what this trailer can hold (weight). If anyone knows how much a cubic yard of leaves wet and dry weigh that would help.

Obviously I would like to built it as tall as possible to fit as much as possible.

Also If...

Leaf vac set up