Another method that I have certainly not tried...is to:
Build your cradle in one foot or 18 inch segments....then.....
tie the boat to a very stout tree..
Drive the trailer forward a foot....
slip your cradle portin A under.....
drive another foot, and on and on.
I don't know if I would try it..but you could then bolt the sectioned cradle
together. As you say, you got trees, trees, trees, and bolts...Seems like
that would work. RichG