Unfortunately I'm not a big fan of bowls... kinda like Pottzy hates puzzles... I make 'em (puzzles) just to stir him. However, your mention of thread chasing got my undivided attention. Wooden threads have always fascinated me and I appreciate your Alan S. link... one of those things I never got around to follow up in the past... still didn't endear me to bowls, but I appreciated the tutorial... liked the way he rough cut segments and made them work... tad cheaper than my Mitreset.
If your first cut is too short... Take the second cut from the longer end... LBD