I was the same way for years, always cranked everything down flat in the press before sewing. Then I tried my mentor's trick on a batch of small chapbooks with 80lb text and just tapped the spine square and started sewing. The thread pulled everything tight on its own and the spines came out cleaner than my pressed ones. On heavier paper though, like a 100lb cover stock, I still nip it a bit or the sections want to slide around. So yeah, it works, but the paper weight and how many pages per signature really change the game. I have not touched the press for anything under 90lb since.