Now I know why 904 was having issues

Oh I get it; using a cup to keep the lips up tight. Or maybe a belt.Yeah, so, if I ever need an alternate method, I'll try to remember this freezer trick.
I think it was TH350/400s that have at least one blind install. It's been a lotta years since I built one of those; over 30 Ima thinking.
Thx TB