I haven't done it but I really want to. I'm intrigued by the idea of a tilt bed gooseneck trailer. If you're going to build (or buy) yourself a trailer I have a couple suggestions for you. Go at least two feet longer than you think you'll need and make sure you have a TILT BED!
You don't need to give up two or four feet of level bed for a beaver tail and you don't have to mess with ramps EVER. I have a an electric hydraulic tilt bed with a 22' floor and an 8,000 lb. Warn winch with a brake. From the time I have my tractor (or car, truck, whatever) at the rear of my tilted bed I can be loaded, tied down and secured on a level bed and pulling away in ten minutes!
Now, I know that doesn't sound like much, but when it's snowing, raining or sleeting in subzero temps with 30 mph winds it means a lot. Another plus with this system is that I don't have to climb up onto a wet, muddy, snowy, icy bed. Just some things to keep in mind.
As to plans and where to go for some good advice on building one yourself from people who've done it and may well be doing it right now, try this site provided by
Hobart. They have some great info and people there just like here. In fact, you'll probably see some familiar faces and even some of the same screen names. /forums/images/graemlins/cool.gif
Good luck with whatever you decide. I hope this helps. /forums/images/graemlins/smile.gif