Since as you say you will never really use it I would seal it all around and once you are successful with stopping thr leak then just shut it and forget about it. I am not a fan of sun roofs and I would never knowingly pay for them or even take one for free if I can help it. The roofs are a very important structural part of the cars and while many will say sun roofs do not make anny difference I being a frant end and brake mechanic can tell you that these always weaken the structural support of all the cars they are on. Can they get by with this lesser support É Yes most do . But if you are a serious auto geek and want to build the motors you will forget the sun roof completely.