Well after avoiding doing the dovetails and mortise and tenon joinery for the apron of the workbench for three months (or so) and after purchasing two new dovetails saws (PAX and a japanese dovetail saw from Lee Valley, or maybe if was Garrett Wade) that could cut through dovetails in 2 inch thick stock and trying various ways to cut BIG dovetails on pieces of 2x4s I finally bit the bullet.
Now the reason I put off the apron joinery was because a) 8/4 stock is not easy to come by nor what one could call inexpensive and b) cutting a dovetail on something over five feet long is very different from doing them on a drawer side.
Here's the joinery I'd been putting off. The Twin Screw Vise end is 2" thick by 6" tall by 24" wide, the other end is only 3 3/4" tall. The total length is a smidge over 5 feet - without the twin screw vise jaw which will add another 2 1/2 inches. Not massive but adequately "hefty".
Normally I cut the pins first then mark the tails from the pins. But when you're playing with tails on the 5 foot long pieces that just wasn't going to work. So I decided to cut the tails first - on the bandsaw. Worked great on tests done on pieces of 2x4. However, when you're trying to bandsaw tails on the ends of something 5 feet long and 2 inches thick it gets a little trickier, even with a larger table on the band saw and a ball bearing roller stand supporting the "hanging way over the edge of the bandsaw table part". Was sort of like trying to bandsaw while on roller skates.
The resulting dovetails aren't light tight - but they work fine. Will probably shim the gaps and call it good.
So here's what I've got at this point. Still have the dovetail to cut for the shoulder vise arm but that'll be easy because the parts ARE NOT FIVE FEET LONG!
For the curious, the apron's ash- about $90 worth.. Sure is nice to work with hand tools. Paring "to the line" was a joy with this stuff, unlike oak. Not as easy as mahogany but still nice to work with.
Next up - mounting the twin screw vise to the right end cap and then it's route dados for the plywood splines, cutting the maple laminate top and figuring out how to secure the shoulder vise. How I'm going to connect this top to the base will come to me when I get to that point.