Oh man I came close to giving in to temptation today to find a power cord for the lathe motor and fire it up, but changed my mind (thanks to the steadying influence here on MM) to do the right thing -- and work on the right hand bench.
So I scooched that one away from the wall, cut out a backing sheet of plywood, screwed that in place. Made 3 divider panels (only half height, this time, since I want space under to slide in plastic bins of greensand for casting).
I attached those panels, but didn't add 3/4" square drawer slides like I did last time, since they will carry shelves rather than drawers, and I wasn't sure how deep I wanted them yet. But with back panel and dividers in place, I could move the bench back to the wall permanently, and finish the top.
This bench is lower and will be wider than the left side bench. The shed door is offset, so a wider bench is possible. I added a 2x8" to the 2x4"s on the top to widen it further. This had to be cut back, in way of the chimney. I did that, and fastened it down, and called it quits for the day.
Like the other bench, this one will be covered with 1/4" hardboard, screwed down, so it can be replaced if it gets too beat up and ratty, some day. One sheet will more than cover both benches.
I'm getting close to being able to fasten down the lathe on the bench, and move the motor to narrow the footprint. And after that, metal work again!