I'll just add that lateral is the single most "feel-able" adjustment for me. I can bowl with spans several fractions of an inch apart, but if my lateral isn't set up correctly in the thumb, I get hand pain and have problems at release.
To illustrate, I bought one of Jeff Carter's old balls he was selling here once. His span is only 1/16 shorter than mine, but his thumb lateral is about 1/8-3/16 further right. Our thumb sizes are very similar (I had to add just a couple of pieces of tape to get it snug), but when I took it out to throw it, if I didn't make sure to come around the ball, I was hanging up so badly that I came close to hurting myself. All it took was to change to a thumb slug with my lateral in it and all my problems went away.
Jess