I had ping-pongs on my 18.
They are kind of noisy but now my wife and I associate that noise with sunny afternoons hanging out at anchor in Cape Cod Bay. Never found the noise annoying.
Boat lived on a mooring, and for 5 years they never gave me an issue.
Cleaned them at haul-out in the fall.
I had mine over flush glassed-in fiberglass tubes though, not thru-hulls.
On my new 23 Sceptre I used these:
https://shop.hamiltonmarine.com/prod...air-29435.html
Also over flush glassed in fiberglass tubes.