The mustang footpocket is an interesting idea worth persuing further, but I too am not convinced its the answer to the mysteries of life. Also I agree completely with your assessment of Andronov-style footpockets. Price of an "Advanced" (this actually means something quite specific in monofin style) monofin from Leaderfins: 129.00 €. Price of a Hyper (non-pro) 259.00 €. Only difference: Footpocket. And that's not even custom pockets, for that you pay 379.00 € like me for the Professional model! That's and extra 250.00 € just for the footpocket...

I'm very happy to share any knowledge I've picked up around the place and there's always room for one more pair of fins in my bag!