Thor, I assisted the crew of Circus this year in transporting their J/30 to/from the J/30 Mid-Winter in New Orleans this year.
I took some photos that you can look at here:
http://www.defiantracing.com/album/thumbnails.php?album=3 I think it really depends how far down the keel box is on the trailer. Circus has their mast under the bow pulpet.
How that this helps you out.
Bernie