I know someone who had white bedliner applied to the areas that rubbed when beaching and it works really well and is not noticeable. I guess the only downside would be if you ever wanted to remove it? it was on a deckboat with a white bottom and had zero performance affects when on plane.
I have the Gibson mufflers and didn't notice any loss in power on my 525, maybe 1mph tops. I know they have a few different sizes, maybe yours are too restrictive for your motor?
I have had good luck with 3bros and I only use Malcolm smith for buying parts (service is questionable) I think Z Racing turned into OC Ktm and they are in orange somewhere, no experience personally with them but some friends I know will only use them. Now that I read this I don't think I am any...
Mike was awesome to work with when he did my upgrade a little over a year ago and I just found out the other day that the service doesn't stop after he gets paid.....haha. I had an issue with an amp (not his fault)and Mike took care of it right away. Top notch service and my boat sounds awesome...