Hi-Lo deviation indices — which ones actually matter for a 6-deck game?

[BlackjackPS]

I've been practicing Hi-Lo for a few months now and I've got the Illustrious 18 mostly memorized. But I'm wondering — for a typical 6-deck shoe with decent penetration (say 75-80%), how many deviation indices do you really need to make a meaningful difference?
I've seen some people say the top 10-12 are enough, others insist on all 18 plus a few more. I mostly play S17, DAS, no surrender games. Also, how precise do you need to be with the TC conversion? I find myself rounding to the nearest whole number but I've read that flooring is better. Would love to hear what actually works in practice vs what the books say.

 

[gronbog]

This book (THLCCS) ranks all the index plays for a wide variety of rule sets and tells you exactly how much each gains in terms of SCORE.

The Hi-Lo Card Counting System: A Complete Guide To Index Play

There is value to be had beyond the I18 or Catch 22. How many you learn is a personal choice.

Flooring is definitely superior to rounding or truncating. Truncating in particular makes the zone around TC=0 twice as big as the others and has you betting and playing the same unnecessarily (and incorrectly) within that entire zone.