Hey Guys- Sorry for the absence. I been chasing the almighty dollah. Gotta pay for those e-bike parts.
First of all, yes I have the adjustable sheets tutorial up. The url is: http://www.backusstudio.com/gng/
I've posted this over on the main GNG thread but I'll repeat it here. I've developed and I'm getting ready to have made adjustable bottom bracket sheets. They should be available by mid February. I'm also working with a pulley and belt manufacturer to have custom 20mm wide pulleys made for the GNG that are as good as we're going to get them. I'm enlarging the driven pulley from 80T to 100T. That's 25% more primary reduction. The tech also recommended AT5 belts rather than a HTD belt. It's still a 5mm pitch but is "much stronger".
I'll have this drive setup manufactured and try it first on my own bike. If it still doesn't work I'll give up and convert to chain. If it does work I'll make the pulleys and belts available to anyone who wants a set.
Belt drives work on everything from racing Karts to computer drives to heavy industrial machinery. Matt Schumacher makes them work on his own custom e-bike drives. There's no reason a properly made belt system shouldn't work on the GNG.