I second the visit to the rental place.

Rental equipment usually gets abused severely and the trailers they use
have been tested under fire.

Take a good look at how the understructure of these trailers are laid
out.

A couple of points..

Use open members...any closed member will collect moisture and salt and
will rust faster than you will believe.

Use similar metals....I have seen different metals combined
(steel/aluminum) and unless you properly insulate them you will see
corrosion occur.

Every pound counts...as you have noted, every pound in the trailer
detacts from what you can haul.

Over build for capacity...it is human nature to overload a
trailer...allow for it.

Avoid unnecessary addons...a spare tire, a tool box, an end gate, heavy
side walls...they all add unnecessary weight. Most can either be built
of lighweight materials or the items can be detached and stored in the
towing vehicle.

Welding versus fasteners for joints....trailers are subject to
incredible vibrational and torisonal stresses. Bear this in mind when
connecting the members together.

Any other suggestions for Grant anyone?

TMT