If you decide upon construction lumber, you want kiln dry lumber. Green lumber will warp on you as it drys. Dig through the stacks and pick out the straightest, cleanest pieces. Generally, the boards that are sitting loose on the stack are those that other people left behind, as they sorted through looking for better. Be prepared to move them out of the way, and to dig down to the better stock. Be nice, though, and put everything back when you're done.
I wanted the left edge of the jaw of the front vise to be flush with the left edge of the top, the right edge with the left edge of the left front leg. So the amount of overhang on the left depends upon the width of the front vise jaw. The width of the jaw is, at a minimum, the width of the plate that supports it, but it's normal to make the jaw extend a bit beyond the plate. How far? The more it extends, the deeper a bite you can take with the edge of the vise, when, for example, you are clamping the side of a board being held vertically. But the more it extends, the less support it has. I decided to extend by 1-12", which gives me a 2-1/2" bite, and which should still provide solid support, given that the jaw is 1-1/2" thick. This means the top needs a left overhang of 12-1/4".
Another wooden item that I love very much is a beautiful mobile holder. You can see one in the image below. These things are not only beautiful, but they can comfortably hold any sized mobile and ensure proper safety. Another amazing thing is that they can be built in many shapes and sizes, as and how you need it. You can see some more examples at the source below
I don't see anywhere you mentioned the over all length of the bench top. A piece of 1 1/2" x 25" x 8' glued edge oak at Lumber Liquidators costs $192 including tax. Two piece is almost $400! Would that be better if I use two IKEA 1 1/4" x 25" x 74" solid Beech ($99 each plus tax) on top of a layer of 3/4" Birch plywood. That would be 3 1/4" over all.
The book is well written and easy to read. The illustrations, I'm sure were excellent in 1914 and, are still adequite now. Most of the designs seemed repetitive, though. I wish more attention had been given to lashing materials. If you are looking for that you will find almost none here. The book was fun to read and provided enough inspiration to make my brother and me attempt a large hut.