fuel tanks and bullet silencers

[renken runner]

I have an aluminum tank that probably original to my '76 Renken open bow. I just pulled it out and am thinking of going to the new cross-linked polyethylene tank. Any suggestions or thoughts either way?

Also, I keep seeing these things called ski boat bullet silencers. What are they, where are they mounted and are they worth the effort of buying and installing? Thanks in advance.