Hi cantSUPenough. Yes the blocks are very usefull. The back foot block is great & easy to feel that my back foot has gone far enough back. The front foot block was a little high & felt a bit slippery so marked some grooves with a sharp knife. Feels good now.
By reading our posts on foot placement & watching heaps of videos.
I found that most riders have, & talked about the back foot being directly above or just behind the mast. So I put my block one full width of my foot behind. I have in fact placed my back foot behind the block too when trying to pump in small waves which felt ok too.
Once I marked the position of the mast on the deck, I then stood on the board in my natural surf stance & marked the position of my front foot. Although I decided to place the block a little more in front due to thinking I need the front foot weight to help push against the upward force of the foil. But this may not always be the case as I have found that the more you put your front foot forward the more your centre of balance shifts further back. Thus making your front foot down pressure lighter. But I may compensate as it is my front foot that is placed first which I can easily slip back behind the pad, currently my foot sits on top. So I think marking your natural surf stance from the back block would be quite satisfactory.
And oh, I have noticed most foilers have the ball of their front foot on the board centre line & not their arch. So my front foot block was placed to do the same.
So far very happy with the pool noodle blocks. Very cheap & haven't budged by being glued down with hot glue.

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