BIG thanks to all for their helpful comments, except for Mjc1973's about sending the wounded Techno to him--although the free shipping offer was thoughtful
I tried the simplest approach first and it worked. That was to loosen the pivot screws on opposite sides. The first time I did it the blade was centered perfectly, but unfortunately was so tight it wouldn't open. Then, by very gradually adjusting back and forth I got it about 98% centered with very smooth action. And I can identify with 98% centered...
Here are a couple of photos of the new backspacer, and thanks again.