The last time I tried to rush on this project, I just about screwed up the legs while trying to cut their tenons on the table saw. Over the last couple of days, I got back into the shop and basically treated these like I would a handcut dovetail layout and preparation. Since I don't have a good workholding surface at this point, I've gone back to simple tools and simple solutions. First, I took the two front and two rear legs through the surface planer so that each pair has the same width and depth. The lengths were already accurate. Once that was done, I used hand tools to fix the tenons. Since I glued the legs up from planks of varying thicknesses, I ended up with tenons that are not exactly the same distance from the front and back of the legs. Instead I focused on the side to side location of the tenons, and making sure that the shoulder is accurately at the same depth all the way around on all four legs.
I got them to a point where they won't embarrass me when assembled. The tenons, though differing sizes, are all square and beefy enough to hold offset pegs. And in any case, the exact locations of the mortises for these tenons will simply be traced from the tenons themselves after I assemble the whole undercarriage into one assembly. I'm still working on dimensioning the boards for the stretchers. Since I have no boards thick enough to function simply as stretchers on their own, each of the four will once again be a glue up of a wide board and a thinner board. I probably need to sharpen up my planer blades. This maple is HARD.