Looking forward to Halls, and Pipe-sters answers.
All I remember when i bought my LT500 back in 88 OEM was rubber bushing/sleeve insulator, I went with a Bills pipe and Answer silencer for 15 years with no problems, I just run rubber washers on each side with a Fender washers over that, I know FMF silencers use a Alum/Rubber isolator, on my own projects I looked into these Versa-Mount Vibration-Damping Mounts (Mc Master Carr) Versa-Mount Vibration-Damping Mounts
 cheap enough, you need a .800" hole for them, been looking for months for smaller ones that you can use a 8mm bolt.