Jay I have used the one that hooks on the down tube and supports under the BB. But I do not recommend them, at last years Cirque their main draw back was demonstrated when one bike was bumped into and a line of 5-6 bikes all using that support went crashing down like a row of dominos.
The type I would like to find is the one that supports the rear wheel and has little wheels that allow the bike to be easily moved around.
See the link to this picture posted by Steven Maasland:
http://album.foto.alice.it/
Unfortunately this is not Stevens bike, but if he or anyone else knows where I could get my hands on some please let me know, I would assume there might be others on the list that would be interested as well
Thanks
John Waner
Huntington Beach, Ca.