Thanks again to SuperTopo for that writeup.
I modified the approach a little. The end seal situation reminded me of the service manual for my beloved '48 Plymouth, whose pictures I ended up pretty much memorizing back in the early '70s. They carefully said to not cut off those overlapping ends of the side pieces, but to let them lap right over the 1/8" protruding ends of the end seals. I did that here, and realized that the ends of the side pieces are made so that they extend all the way in to the main bearing housing. When everything is tightened down, the end seal ends compress, and there's a solid cork gasket surface all the way around the corner - no joints, so no sealer needed. I assembled it this way, with all pieces completely dry, and took it out for a test run. All 4 corners are dry as a bone.
The engine was in the car rather than upside down on the bench, so it was going to be a challenge keeping the side pieces in place while wrestling the pan up & compressing the end seals. I stripped the paper off of a couple bread bag ties, and used the very thin wire to loop through 4 of the gasket/pan holes to keep the gaskets from jumping around. The tails are visible hanging down in the photo. They only needed one easy twist to stay in place, and the wire is so soft I could just grab one end and yank it off, once enough of the other bolts were in place.
