Found it difficult to find a replacement valve for a fiberglass swimming pool (Either commercially or online .STL sites. After many variations and a crash course in threads, got one that is better than the original. I printed it thread down with support. Very easy print. Four walls with 20% infill seems to be working just fine. Test models were done in Sunlu PLA+ and have been holding up so well, I haven't printed in anything different. And I'm in Florida. Fusion file included for variations.

 I hope this helps someone with the same issues I had. Cheers!