Peter Prier pointed out that my corner blocks were too short. I could make up for that by raising the center of the arching by a millimeter, but I decided to take them all out and learn how to properly make them with Juan.
The biggest mistake I made before was gluing the blocks in with a ton of hide glue and clamping them tightly to dry. This meant they were pretty much IMPOSSIBLE to take out--and they're supposed to come out easily when you lift the rib structure off the mold. I had to chisel and hammer and mutilate those original blocks to get them out in pieces. My mold suffered some chips and splinters in the process. Ugh. Luckily the mold doesn't need to be in perfect condition. It's just a gluing surface.
I had such a time the first time around getting my blocks cut to dimension with perfectly square corners all around.
Juan showed me how to do it so easily, teaching me which dimensions are really important. For example, the side of the block you'll be trimming into the shape of the corner--who cares how deep that is if you'll be cutting it away? It just has to fit the shape of the corner, which is pretty small.
Splitting the block wood with the natural grain/split is the most important in establishing your reference side. Everything will be squared to that side so you can chisel the block with the grain and it has the most strength and integrity supporting the violin structure. The top block is the most important because it takes the pressure of the neck.
Apparently some old makers don't even use corner blocks and just glue the rib corners together. Crazy! I think they're crucial to support a violin that will be more durable and long-lasting. But the point there is that they don't have to be perfect. Nothing does, really. That's what makes a handmade instrument unique from its look to its sound.