I don't know if I can be of any help to you guys but a friend of mine has an '06 RSTD and he is on his 3rd radiator. He has had the same problem with leaking. Seems to me that Yamaha has installed some bad radiators for a couple of years. So far he is having good luck with the 3rd one. You may want to check with the dealer that did all the work and is pretty knowledgeable about the problem. Contact the owner, Mike at Cyclesport Yamaha, Hobart, IN. Sorry don't have the fone number...just google it.
I hope I have helped.