Wedged tenon design question

I'm in the process of designing a knockdown shelving unit for our camping kitchen, having discovered some wire shelving bits left over from a guinea pig cage project. These wire shelves are the sort you find in closets and places - I figure I can make a couple of 'ladder' endpieces with holes to take the stretcher wires, that is no problem. The tricky part comes in holding those endpieces together so they don't fall apart, and to prevent racking. The legs are 1x1 1/2 (finished dimension) oak (or ash, not sure - it was free scrap lumber) and will be 22 5/8 inches apart (the length of my shelf scraps). I figure I can make some rails using wedged through tenons to hold the thing together and, if the shoulders on the tenons are big enough, and the wedges tight enough, it should keep it from racking.
How thick should the rail stock be? I've got some half-inch (finished dimension) ash(?) stock that I can use, and can probably find some 3/4 stuff in the drying stack. The through mortises will be centered on the wide (1 1/2) inch face of the legs - I figure a half-inch wide mortise would be OK, but a 3/4 inch wide hole might be too big. Any advice?
Further, I've never done wedged tenons before, so I don't really know the appropriate dimensions for the hole in the tenon, nor how far the tenon should project beyond the legs. At a guess the wedges should probably be of the same thickness stock as the rails, and more or less square in cross section somewhere near the middle of the wedge? And the tenon should extend at least twice the thickness of the wedge? Any advice?

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