Great stuff Mac!
Really detailed info on spring brakes, I had one fly apart on me years ago when it was still normal to cage the spring and replace the diaphragm. It wasn't a memorable occasion, the pot gave way from the caging bolt and luckily it was clamped in a bench vise. so the only thing I could do was slowly open the vise and let it fly, and it did! bouncing off walls and the ceiling. That's why they are clamped permanently now to save lives...
I'm going to post the pdf to my blog and give you a nice credit.