The index for insurance is the single most important strategy departure, and it's also one that can change significantly depending on the composition of your hand. For example, the single deck TD insurance index is +1.4, but the CD insurance index for A-A is -2.4! Quite a difference! Consequently, it may be worthwhile to learn the CD indexes for this play. What makes this unappealing for many players, however, is that it's difficult to learn the ten CD insurance indexes for all of the possible hands.

So here's an easier alternative, which I've found to be very practical in actual play: simply make adjustments to the TD insurance index if you have one or more aces or 7s, 8s, or 9s in your hand. Specifically:

1 Deck
TD index = 1.5 (this is the "regular" insurance index, rounded to the nearest .5)
For each ace in your hand, subtract 1.5 from this.
For each 7, 8, or 9 in your hand, subtract .75 from this.
For example, the insurance index for A-10 is 1.5 - 1.5 = 0.

2 Decks
TD index = 2.5 (this is the "regular" insurance index, rounded to the nearest .5)
For each ace in your hand, subtract 1.0 from this.
For each 7, 8, or 9 in your hand, subtract .5 from this.
For example, the insurance index for A-10 is 2.5 - 1.0 = 1.5.

You could make further and more precise adjustments, but the method described above, I think, is a good balance of accuracy and ease of use.

The data for this is based on Cacarulo's excellent post in the Best of the Masters section of Don's Domain. Take a look at it if you want to see the precise CD insurance indexes for 1D, 2D, and 6D.

David