I have built several dual axels. I also have repaired several production trailers. A Couple of things that I would offer when building a trailer; 1. Over build, people rarely consider how much they are putting on a trailer and include the weight of the trailer in the equation. 2. a lot of people own a “welder” but that doesn’t make it qualified to perform the welds needed on road worthy trailer (heat, penetration). 90% of the trailers I have repaired, the welds looked like bird **** and were somehow holding together. But when they fail from overstress or rust out, you don’t want to be in the car behind it when it happens.
Having said all that here are a few things I have found helpful on dual axel trailers. If at all possible do a deck over your tires, eliminate fenders. if you aren’t picky about looks use rough cut oak, it is very durable and can be re coated several times over. Put as many stake pockets as you can on the sides, they make great tie down points and you can never have too many. I recommend a dove tail. Plus it allows you to step up on the trailer with more ease. Removable ramps that store under the trailer are always a plus as opposed to ramps that are attached on a pipe or hinge that is not easily removed; they tend to get in the way if you are trying to haul something that is at the length limit of your trailer. I also would reinforce a winch plate at the front of the trailer for future winch application. Weld a piece of conduit on the bottom of the frame and run all your wires through it, you never will worry about them getting caught on anything. If I were building dual axel trailer I would not compare the price cost of new or custom built. I would spend the money one time to have it exactly how I thought it would fit my needs best. Realistically it will long out last the POS that is sold for half the price.
Just a few thoughts based on my experience.
Where are you in NC?
Stuk4x4