Help - I do not want to seem like a dummy on this subject, but I do not know how to properly measure the opening portlights on my OD 25. They don't dog down anymore and leak, plus the glass/plastic is scratched so you can't see out and some of the hinges are broken. I would like to replace them with Beckson or Bomar units or something else that will at least hold up a few seasons or more. Is there anyone out there that has done this and can help me with the proper info? I sure would appreciate it. Thanks, Fred