SS thread! Nice. There is this guy, Brian, who rides with us from time to time on a single speed, and quite honestly, I think he is faster than most of my group and many of them have podium placed in the Florida Circuit races.
Anyway, since you guys are talking about SS drive systems, he has a custom TI bike with a belt drive system. I believe it is this one:
https://www.sevencycles.com/spotlight/belt-drive.phpI got a chance to take it for a quick spin and I have to say that belt drive is pretty slick! Lighter, and smoother. You don't realize you can feel your chain until you dig into a belt drive. The sensation is so fluid!
They aren't cheap by any means, but definitely worth looking into. I do know he said something about a tensioner wheel he added to the system as he was having problems with the belt coming off. Since he installed it, it's been perfect.... The guy rides heavy 1 to 2 times a day.... He's an animal, LOL!
Anyway, if you have questions about it, I can get in touch with him and get you more info from his first hand experience.