What Size/Flex for Prior Powstick

I am looking at this years prior powstick, I currently ride a glissade shortbus 165 and a Khyber split 165. I am looking for somthing a little longer for the deep pow, but i still want to steer this thing and charge, the choices are.....176 and 181 and I don't know which sz. to get??? I can handle my 165's fairly well and throw them around, I was also wondering if anyone knew much about the flex, you can add quadraxial fiberglass to make it stiffer for $100 but is it neccessary?:confused: