On that size board you will probably have a pretty static spot for your front foot, but will find there is a range of spots for your back foot depending on how powered you are or what direction in relation to the wind your going.
I ride a 5'8 2014 Celeritas most of the time. Definitely experiment with moving your front foot. If the water is not too choppy, then often times going upwind I have my front foot just off the front of the pad and my back foot between the two pads. This board already goes upwind really well, and if you move your feet forwards it goes upwind even better. It is most important to move the back foot for upwind, though. For making turns, I shift my feet back, with the front foot at the wide point of the board and the back foot jammed against the tail pad kicker. So get some surf wax and coat the spots without pads. It will help you learn to gybe, too.
Agree on not changing the fins. The fins on the Celeritas are good. I don't change them for ocean or riding in flatter water.
I definitely agree on not using straps. I learned to ride a surfboard with them and as soon as I took them off, I wished I had never put them on in the first place. With straps you will have a lot of extra crashes while you deal with the straps when gybing. Also, the Celeritas is a fast board. When I'm really moving on it and crash hard, I'm pretty happy to not have straps on...