I have a 1975 Tahiti Tornado with a 455 olds in it with wet logs and snails. It has thru hull exhaust with rubber flappers, that basically do not cover the exhaust. I want to build new tips out of stainless, I am a metal fab guy, basically I want 4 inch slant cuts for it. My question is do I need the flappers or not, it seemed fine the other day when I had it in the water, do the snails cause a s trap effect? thanks for any help