The slower I’m moving, the more I find I need to have my back foot further ahead of the mast otherwise I’m more likely to stall the foil. If I’m moving fast, then I can pump with my back feet behind the mast.
here is a clip, right before the link turn, I move my back foot further back to be able to push more into the turn. I felt that coming out of the turn I was too slow and so I moved my back foot forward to avoid stalling the foil and to give a chance to pump away.
How this relates to your question - the position of the mast in your board doesn’t matter, as you’ll move your feet around (you should move your feet around) in a way that gives you the correct feeling for that context. Swing weight is incidental really for small prone boards.
The only thing that mast position does make a difference is takeoff, if the waves are powerful you can have the mast too far forward, and if the waves are weak you can have the mast too far back, but this can be overcome with a bit of adjusting the takeoff, and will have little to no impact once you are up and riding.
What does make a difference in making pumping easier is a baseplate shim, thick end at the back, which changes the angle of the board relative to your foil and can make a big difference