Update: Against popular recommendation, I've installed the port into my fresh water tank. It seems to be what all the RV'ers do, and I could not locate a specific RV/fresh water tank port. So I used the one I linked above. The tank is enclosed with fiberglass on all sides and screwed down wood on the top, all of which should significantly reduce flexing of the tank. After installation and filling the tank, without the wood on top - the top swelled considerably and the port leaked just a bit at the O ring. Nothing to worry about as it will simply drain into the bilge - also I believe that with the wood in place and screwed down, the tank will not be able to flex, and therefore cause the leak. I'll update this in the future if I encounter any long term issues.
For me, I can now be 100% satisfied that the water in my boat is safe for drinking and that's important to me. Just disinfecting the water, no mater how effective wouldn't have made me feel right.
Some pictures:
Before:

Why I'm so glad I did this:
Undisturbed (white bits are from cutting the tank)

After moving the water around a bit

Nice clean tank:

After:
