Rex Marine redesigned the flappers in their tips and you can send them back to have them updated/repaired. The new ones are supposed the be much better durability and noise wise. PM RexMarine here on the boards, he's been great helping us boaters out.
I blew out a flapper and they are going to fix it. But, I'm waiting for them to introduce their new tip that incorporates both a flapper, and muffler that will quiet a boat down quite a bit without loosing power.