If that turnbuckle is for belt tension, it's also transmitting vibration to the rest of the device and in doing so its attachment points would be taking a beating. Perhaps it could be eliminated and the idler pulley used for tension, even another added to keep slap to a minimum. There must be enuf hp there to overcome a bit more friction in the drive train. Loosening that connection might also mean a lighter bob needed on the top pulley.
I'm imagining bent rod belt guides similar to those found under Craftsman mowers/decks if slap gets to be excessive.
Among my WAGs, it's conceivable that if steel belted tire rubber was used that metal within could fatigue and leave the rubber less able to hold the screen in position. These would be small refinements if needed at all.
The videos are among the best organized and edited I've seen in a long time. Way better than 30 sec of useful info/shots and five minutes of some guy hollering over the racket while explaining why he built something. IMO, just the right amount of seeing this well executed machine in action. "Two thumbs up!"