Hi there Pat,
Yes, I understand the dilimma. I searched and searched. Like you, I talked to several trailer builders and nobody makes a simple flatbed/DUMP trailer. Especially one with a 20' bed! And there is definately a market for such a trailer, too! An average guy can unload his equipment, then using the tractor to load material on the same trailer...and use it as a dump truck, (within limits)...instead of having to buy a separate dump truck or going back and bringing yet another trailer, (dump), to move the soil or debris. It just makes more sense to have it all in one...for just a few dollars more. But, actually much cheaper than buying the other separate toys. A tilt trailer was an option, but still did not fit the bill. The good news...I finally found a trailer maker who makes these trailers and with the few more add ons I wanted...and that's what you see.
Also, I think that because of the weight shift when dumping...that is why the wheels are a little further back than a normal trailer. But that tradeoff can be worked around with how you load it by keeping most of the heaviest weight in the back half of the trailer...and using common sense. I suppose if you are into road paving and such, you are better off with a dump truck. But, I am just an average guy who likes the versatility of having a dump trailer now and then...even with a shortcoming or two.
I will PM you with more details...