I think it works best to have your weight as much directly over the seatpost as possible. To do that I have to push the seat as far forward as possible (so the seatpost clamps are at the back of the rail adapter).
When I drill a CF seat base that will be used for muni or Coker I put the holes about 1cm back from where they are on a stock seat.
I don’t know if it actually makes any difference. It just seems, in a logical sense, that you should have your weight as much over the seatpost as possible. When you angle the seat up you sit farther back on the seat so the seatpost should be positioned farther back. But in the end it might not really matter. In the end your weight is going to be centered over the hub no matter how the frame and seat and seatpost are positioned or angled. Take a look at the Telford unicycle and you’ll see that angle and such of the seatpost doesn’t affect rideability of the unicycle. The Telford rode and felt like a normal unicycle even though the frame did a zig-zag.