I finished up the metal bashing and drilling on the rear seat riser last night. Tonight I deburred and dimpled the holes. This shot was taken before I dimpled the holes. You can see the shim I needed at the front end of the rib on the left end of the wedge. I needed the shim because the one inch wide bevel at the front turned out wider on the left end than the right. Grumble grumble.
Here you see the bottom of the rear seat riser. The plans call for four ribs, and a width of 17 inches. At first glance, you would have the ribs evenly spaced. But that would have none of the ribs lining up with the ribs that support the cockpit floor. I moved the two inner ribs further apart, so they will lay right on top of the two ribs that run under the rear seat. That seemed much more sensible. It also makes a small area under the middle of the rear seat riser that I can use for storage. The length of unsupported 0.032 skin between the ribs is no wider than the width of unsupported 0.032 floor skin that the seat cushion is designed to sit on.
I've still got to mount a piece of hinge on the back to secure it in place, but I need to mess around in the rear cockpit to figure out the mounting details. So, that'll wait a day or two until we break out of this cold snap. I'll prime the parts and assemble them once it warms up in the spring.