Welcome to the forum, it's so nice to have a fellow Kiwi in the mix. I'm glad you have a build diary as we all have different ideas on materials and construction concepts and on many an occasion I've thought, "wow brilliant, why hadn't I thought of that!" At the rate your build is going you'll be completed before I'm even a third of the way through, and I've been at it for years. Cheers.

Hello,   Do you mean the hysteretic oscillator? https://www.allaboutcircuits.com/textbook/experiments/chpt-8/555-hysteretic-oscillator/   Bertus

Hi all   I recently became aware that the file I had designed in my 2005 Slat Pack was quite off. I sat down to redseign it tonight, but what a headache it caused! I found it quit a chalenge, especially as the sloped cutout has such tight clearance to the rear, where the upper band sits aginst the rear of the slat. I've attached the file here and I'd welcome feedback on the design, It's just not sitting right with me! My main concern is the clearance between the top band of the shoulders and the inside of the angled part.   I designed it to 3D print on its side, at least that's the best orintation I could think of...   I've attached an STL as well as my Solidoworks file and a few screenshots, the last one being my intended print orientation.   THanks in advance!   Fixed.SLDPRT Fixed.STL

That's correct.     You are building the naked inner shell of the shoulders (B).   Upon which, raised bands A and C (and finally D) will be built.