[C320-list] Emergency Tiller Port/Hatch

[Dave Hupe]

I replaced my emergency tiller port in 2017 after discovering that it was the source of a big leak.  I used this https://www.catalinadirect.com/shop-by-boat/catalina-270/hull-deck/cockpit/inspection-port-8-38quot-od/ .
The replacement helped significantly to reduce/eliminate leakage into the stern.  However, the seal was not very tight to begin with even when new, and I'm getting a fair amount of leakage again.   
Has anyone found a better port/hatch replacement?  I'm thinking one with a screw-in cap might be better to get a water seal (although I understand it would be more difficult to remove, especially if not opened routinely). Ideally a replacement would mount using the same mount holes (I know, I'm dreaming). 
Dave Hupe
1994 C320 (#32)
Holland, MI