@ +2...
...the undealt composition of cards begins to favor doubling 9 vs 7, due to a higher ratio of 10s and Aces. Notwithstanding, I would make a few 'risk-averse' alterations to the published Red7 1-2D indices -
9v2= +1
9v7= +3
10v10= +4
10vA= +3
If you alternate between handheld and shoe (6-8D) games, simply double all 1-2D index values.
The two beauty factors of R7 is that its the easiest level-1 system yet comparable in performance to more complex systems -and- it can be 'upgraded' to a pro-level-2 system over time WITHOUT ever changing count systems.
G