How about more, detailed pics of your trailer builds!

[Izzy]

If you want some pointers I'd be glad to share some thoughts. Here's a few thoughts ro start

In my experience, Our trucks and trailers in stock form are not scale. And not width to height to length.
Additionally, getting stock or aftermarket suspension systems tends to be the lesser cost avenue.
Styrene is good, I like .08. Has good body and yet not too thick.

Balsa is a good choice too.

It really depends on what you want to do with the trailer - how much abuse.