Have a look at this video, Devon Malcolm surfing a 7’2 (so same length) Look at the slow mo from about 18 seconds to the end of the wave (about 20 seconds long). Watch his back foot - the top turns and it’s way back over the fins. The bits in between the turns and it’s about 2 foot in front of the fins. [at 28/29 seconds, after the top turn when heading down, you can see him move his back foot forward quite a lot]
Your back foot needs to be going up and back all the time - planting it in one spot (too far forward or back) and it limits what you can do on the wave
http://foamsymmetry.com/now-playing-dev ... ik-derman/
(Btw, if you do just want to take off and do lots of turns then go for it. But to maximise the wave, as wkk says, you need to flow in between the turns, build up speed and set yourself up. As shown in the clip above)