Sorry Dude, I didn't see the Twins, I thought single. Your right on.

By the way, i've replaced my Eddie Marine Flappers twice in two years. Who makes better ones.

All good, glad to know I'm not completely crazy.

What kind of flappers do you have now, rubber or internal stainless? if they are rubber you might be SOL.

And I guess the last question is do you really need the flappers. I don't run any on my boat, but the exhaust is mounted pretty high.

Like these guys said; make sure the tips have the internal metal flaps. External flaps alone will not be adequate for that set up. Also, don't beat yourself up trying to work with the old hoses. They look like they'll be old and stiff as a preachers *****. New hose is a bit pricey but it'll make the job a whole lot easier in the long run.