Went back with PVC
I replaced my ports on a Hunter 28.5 windows similar or the same as your 31 with PVC. The way I figure it, my 1984 boat is nearly 20 years old...that's a long time for a PVC port.I went to West Marine and bought new windows...unfortunately the windows were not an exact match. I had some minor fiberglassing to do because the new windows did not match the cutout of the old windows.The long window I had new frames and windows built by Mark Plastics in California...I used silicon to seal the window.Mark Plastics369 East Harrison StreetUnit G.Corona, Ca 92879909-735-7705He did a nice job.For original port window parts go to www.pompanette.com. You can find replacement windows which will be an exact match for the existing cut outs.