Listen to Graham on the needs of the sprag clip. Every tomos needs it, no matter the speeds. But especially on tuned fast bikes.
For shifting especially on a tuned tomos I will always release the throttle at the shift point then gun it again once the connection is made. Just helps things move a little smoother.
Ryan from Cranks is machining tomos gears. He said it would be about $150 for it all said and done. The ones he did recently look amazing and have like half a mm in tolerance, before he started they were jumping about 3mm difference. I'm sure a nice balanced setup like that would make worlds difference. It is on my to-do list for sure.