We are having a Harmon installed where we used to have a wood stove. The venting pipe will be 12 ft from start to finish but there will also be two 45's. I understand that means my length will really be 15 feet since factoring in the 45's increases the length. So we are just at the maximum length for using 3 inch ICC Pipe. Since we are at that limit should we consider using 4 inch just to be sure we have less flow resistance? You know just to be extra vigilant? Will the stove be more efficient in general if we do this?? Also is it really ok to adapt to the old woodstove box and chimney rather than run new pellet pipe all the way through the ceiling including the chimney? Will that adaption from 3 to 6 or 3 to 8 (not sure which it is yet) be ok with the fire regulations?