Hello I have a question regarding the carbon stringer. Do I use one up center on bottom and one up center on deck , or use them as parabolic stringer on the rails, or on bottom running parallel with each other a few inches apart from tail to nose.

All you need in one carbon strip on the bottom. Carbon stiffens the board and only works in tension, so on the deck is pretty useless. 

Laminate it right down the middle of the bottom and you're good to go. You can immediately lay out the bottom fiberglass, cut, and laminate right after the carbon strip. It's best to laminate the carbon first separately to eliminate air bubbles.