[hiccup]

        Yes, you're 100% correct.  The main differences between the old & new portlights are the seal and then the hinges are changed so they work with the new seal.  The new seal is, as you mention, much thicker in depth so that it can compress more as the window is closed.  It also has a secondary sealing lip.  When closing the window you can clearly tell that you are compressing the seal a great deal more.  After looking at the new and old next to each other I have decided to replace all 6 to the new style.  No sense in going to the trouble of re-bedding an inferior portlight that we all know is prone to leaking.

Here are a couple pictures of old vs new