honestly man im always messing with different positions
doesn't really seem to matter
a lot of times, especially if its a really long fast spin, my front foot starts off around the bolts and slides closer to my back foot throughout the spin.
I do recommend you mix it up a bit. Try really, really slow manual spins, try spinning as fast as you can sometimes too.
It'll help because throughout a manual spin there are really two ways of balancing.
When you are going slow you are just balancing a manual. But when you are spinning fast enough its more just about keeping your centre of gravity and pumping with your hips.
dont forget to use your arms, you can tuck in, spread out, crouch, stand straight. You have to kinda just get the feel for it and just do whatever you need to do throughout the spin to keep it going, the initial placement isn't that important, besides just getting a clean, controlled start, dont forget to prewind.
I will say the biggest thing is having the confidence/balance to prewind,lean into it and spin as hard as you can and pump throughout. You can get a lot of rotations in before balancing/pumping even comes into play if you spin fast enough.
Dont get too discouraged man. I've been manual spinning for like 8 years and there's still days where they just dont work haha