Further to that tiny vid, once on a runner does this foot position look ok or should I try to go even further back?

Loz79 said..
You really should only move back if the runner or bump you are on is going to cause the nose to bury. I try to keep as far forward as i can especially in smaller runners and only move back if needed (for stability and to stop a nosedive) if you move back too early then you will start to push water and slow down....each board is different with different balance points but trimming fundamentals remain no matter what board you are on

Thanks for the tip.

The other reason to move your weight to the back of the board is to make it easier to turn the board. If the nose is up out of the water, just a little, it will turn easier. This is really something you should practice. If you find the sweet spot it doesn't take much movement (just a small sway backwards) to lift the nose so that you can turn with a quick paddle. (I need to practice it myself...) This especially works when you have to paddle around a buoy. If you are downwinding the same principle basically applies - you need to get back to turn on the wave.