I used a Condor portable motorcycle chock on the streetglide. on the cross bones, i simply cut up a 2x4 into short pieces (about 1 foot) and used deck screws to mount them on either side of the front and back tires (into the wood floor of the trailer, not into the tires..ha) so that the bike wouldn't "walk" side to side. You'll get a lot of free advice on securing bikes to trailer them, so here's mine -
secure the bike upright with ratchet straps but don't tighten them down to where the bike can't bounce on the shocks. don't have the kickstand down, you don't want anything rigid in contact with the trailer. double strap the front of the bike (strap it once, then put a second set in another location so if one strap breaks or loosens you'll still be secured), and finally, once you have the bike secured on the trailer and head out, stop within the first 20 miles or so and check all of the straps and see how the bike appears to be riding on the trailer. obviously, you should check everything at each gas stop also.
here is a photo of my bikes the day i left.
https://picasaweb.google.com/1042538...eat=directlink
hope this helps.