Here is one I found that is a 20' w/4' dovetail with fold flat ramps. The link shows a GN but you can get it as BP also.
7 Ton Gooseneck & Pintle Trailer, Johnson Trailer, Colfax Wisconsin
If you are going that big, get the 2 x 7000lb axles.
7 Ton Gooseneck & Pintle Trailer, Johnson Trailer, Colfax Wisconsin
If you are going that big, get the 2 x 7000lb axles.