I just put a set of Avon Cobras on my F6B as well. They have been excellent on my 2 old Valkyries so I figured why not give them a try. I did wear out 4 rear/3 front of the OEM Bridgestone tires and liked them just fine. My only minor complaints were that they squirmed around a lot on tar strips, and they didn't last as long as I expected. So far I'm very pleased with the Avons.
I have had great luck with Michelins in the past on an old BMW. I like the idea of a 65% aspect ratio as a little bit more cornering clearance would be nice. The only thing that would hold me back is the bias ply construction.
I'm running Avon Cobras but would be happy with E-4s also. I have a Yamaha Venture which runs bias tires and no problems. I would not mix a radial and a bias front to back. Do not see much advantage to a 65 over a 60 series tire. What is that less than a millimeter?