I have never glassed obeechi but covered it with oracover. I covers quite nicely and is wonderful stuff. But I can see what you are saying. It might be worth giving a light seal coat like a sanding sealer used in woodworking that you could sand with 220 before using light glass. If your layup schedule is several layers of glass then it may not matter. I assume you are doing light glass for just a nice finish ala JHH kits etc.

As for the hinge, I see. Except I would recommend a fine triangular file. might provide a sharper groove.