thanks a lot for all your replies , just one more thing.
I am honestly talking do not understand the "open class" rules regarding obsolete cats like my P19 , H20 .e.t.c. Andrew mentioned about Tornado sail plan on prindle. is it acceptable from "official" standpoint? P19MX + spi , or another p19 with huge hooter? racing rules of our club state that any cat with a Portsmouth rating could participate ? so I guess this sort of modifications is not acceptable for cc racing.