Blood, do the primary problems with the Large Turbine happen to center on the Optimal Flow logic?
I've been looking at the code, and I can't help but wonder if timing is always going to be a problem when trying to handle this. Specifically ensuring that you always have "only" the optimal amount of fluid after deleting the extra fluid. Since the GT hatches were never supposed to work this way (they're supposed to act as buffers) it's one of the first things I'd abandon if you can't get it to work right.
Its kinda neat but doesn't really add much to the game, especially since GT doesn't actually provide any way to throttle flow rates other than a few pipe tiers.
Oh, idea: screwdriver on a pipe-cover to throttle flow rates :p