Phil,
I talked to my riding buddy this evening and he has a 14', 2, possible 3 motorcycle Haulmark trailer. I asked quickly, before I forgot what I was supposed to ask him about (51
) It has a rear door that opens down into a ramp. I've seen it, well built, sturdy, lots "O" features. I guess you can go to this page and design one for your needs. I believe he paid around $2k. But then you can use something like this for lots of applications.
http://www.haulmark.com/classifieds are a good source also.
John
