When I've finished it I'll take a snap, but don't hold your breathe, at the moment I'm a very long way from completion and as I've said already I take things painfully slowly to make sure its done as accurately as possible. We also have a two day photo trip to the Seven Sisters Country Park this week which is not going to speed things up.
Your supports sound an excellent idea. I prefer the idea of supports attached to the vertical sides and thus spreading the load around the structure, to all the strain being taken on the top because wood is poor at dealing with bending forces. From your picture I imagine the load would also be vertical, with no wire pulling at an angle? Even better if thats the case.And no more weekly trip around the house straightening all the frames!
I've been discussing the mount colour with my wife based on all the feedback and the compromise is a pale grey (The image is of South Dorset, Chesil Beach and the Fleet, so a mixture of reds, browns, greens and blues). I propose to leave a small white border of around 5mm around the image which I hope will help project the image.
Sorry, I'm unrepentant about the joint construction. The stresses and strains on a racing dinghy are far more than a picture frame will ever have to withstand although they are generally designed to spread any point loading into the structure as much as possible.