You hit it right on, IMO. I'm approximately 1/2 to 1 shade lighter with my IE than their chart shows. I've felt like calling them before and mentioning I thought they were off, to dark, low value. As an example A2, try 1.5 (main inc) and 1.0 (for inc break up and ridges). In the 70 dipping liquid series, they have the 6.0 and the 6.1 versions. I think one was made for Beyond, and the other for Plus. I don't think they're to far off, but just confirm what you have and what they suggest. Talk to Steve or Rich.
I may use 3.0 on a A4, 5M1 etc, or where seen, but I hardly use that one. I don't do a lot of dark shades routinely.
Remember, you can dilute the dipping liquid with distilled water, as they're predominantly water based.