Setting for index on a single day is pretty easy. I have experience using a bolt. My old 63 Dodge with a crossram had 3/8"x 24 bolt style stop. Could move it .01. Here's the trouble with the bolt. It's not linear when it gets cranked out 45 flats on the hex or so. The amount of ET drop depreciates rapidly. So when you get into that area you don't want to move it. With this intake and Eddy carb's that was an issue. Here's my problem with that. We may run over a period of days on the same weekend. If you get a big weather change the bolt needs to be moved. Now all the weather data vs bolt position changes. Many Sundays there is no time trial. Now your guessing. Thats why on long weekend we may chose 9.25 over 9.00 so we have enough in the bank. I'm not convinced timing is the ultimate answer either. For sure weight alone works. But a big swing can put you in 300lb territory. That's more than I fell comfortable with.
Doug