I wouldn’t recommend 860R for a newish prone rider. The R is a little technical pump and wants some speed, not something I would recommend for you at the moment, hold on to it though for later if you can. The 1130S or 1300S would be my rec for a new prone rider.
What kind of waves are you in and location?
I’ve had the 980S, 860R, 1075R, 1300S, the 1300S has become my daily driver for prone.
Golden rule: move your feet into the sweet spot while you’re on the wave, before your first turn. If you are at the end of the wave, get them right for pumping before you kick off and start decelerating, as it gets much harder to trim your feet once you’ve realised they are too far forward to pump