In looking at the US Sailing portsmouth tables I am confused. I have a Hobie 18 magnum. Am changing to a 29'6" stick, from a SX. Will be running a Tiger main and spin. I believe the main is no more than 5% larger so a .995 d-pn correction? Table states Hobie SX-18 spi. The tiger spi is less sq area than a SX spi, I think. So dp-n of 71.3 + .995? Will take the wings off to race. Please help me get this right so race officials will not get upset if I am wrong. Everything else will be standard Hobie production 18 parts. Downhaul and main purchase will be at class limits for 18SX.