Thanks Richard for the thorough review!
Yes I could make the supports longer, there is space. I did build an almost exact panel 20 years ago (I still have it) and it held up very well and super strong, but in that version the top panel was permanently glued/attached. No hinging. I will look into making the 2 supports longer.
I was thinking of a simple set of hinges under the front lip. It cannot be seen from the standing or sitting position, so im not too concerned about the cleanliness of it. Alternatively, I may just screw the lid shut from underneat, in a way that I can easily maintain in the future and open up.... this wont happen often, so a hinge is probably overkill.
I made it all in solidworks and yes I already have the angles laid out!
regards