Well, I've been wrestling with the idea of doing an 8x10. I was going to hold off a year, but a week or two back, the devil made me buy two 8x10 film holders off ePrey. My easy way out would be to upscale the 4x5 I built two years ago but I am considering some "enhanced" designs.
Among my thoughts, a two-part body, at least the larger part with sloped sides, such that the design and focal length could be altered without a complete rebuild. The heavy rubber bands on pegs seemed adequate to hold a 4x5 holder, but I'm leaning toward a sort of lid assembly and catch for 8x10. The previous box was mostly made from scraps found around the workshop, but with the larger pieces required at 8x10 I may have to actually buy some stuff.
I've tried to organize my thoughts with some drawings in TurboCAD, but I know so little about it and use it so infrequently that I spend more time wrestling with the tools than designing!
My target would be WPPD the last Sunday in April, so I suppose one of these days the contemplation phase needs to transition to construction. Of course I do have three pinhole alternatives to fall back on.