Have you already built your in wall tank, or just getting it ready? What kind of panel do you want? One to get into the tank, light, sump? What is the size of tank and any pictures would be great if the tank is already in the wall.
I have pics at home that i can post tonight... It is fully open in the back. Mainly looking to have access from the front to move corals or scrape the tank... Thinking about a single panel across the front top.
I would go with multiple hinged panels across the front (probably with a vertical mullion to separate them and to prevent light-leaks between the seams). Put the hinges at the top, and come up with some way to brace each panel open so they don't hit your head when working.
The reason I would go with multiple panels, is that I hate installing hinges and I hate (even more) trying to install more than two hinges on the same door and have them be perfectly in line.