Here is a way of improving your Hi-Lo system. The idea is to use a side count of 7's but without learning any new index number. So, you will still use Hi-Lo for playing purposes but your BC will improve from 0.969 to 0.984.
This improvement means an almost 6% in SCORE for 6D.

Now the method:

1) For playing and insurance decisions use Hi-Lo.
2) Keep a separate RC to accounting for the sevens. Start the IRC at -4 * #decks (for 2D you will start your side count at -8).
3) Each time you see a seven add +1 to your Side RC. Another way would be to start your IRC at +8 and each time you see a seven substract +1.
4) For betting you should multiply the Hi-Lo RC by 2 and add/substract the Side RC.
5) With this RC' do the TC conversion as always.

Basically, you should keep two running counts:

HL_RC = Hi-Lo Running Count.
SC_RC = Side-Count Running Count. This one started at IRC.
DR = Decks Remaining

For betting calculate RC'=HL_RC*2+SC_RC ==> TC=RC'/#DR

The beauty of this system is that it is easier than keeping a side count of ACEs since you don't have to change any index while still having a little better SCORE.

Here is the analysis for 6D,S17,DOA,DAS,SPA1,SPL3,NS,5/6,Catch-22:
(I used my own simulator for running these sims).

1) Hi-Lo (5,000 million rounds)

 
play-all | rounds played = 100.00%
spread ev/h sd/h ror% n0 di score ekb avb unit kelly
------------------------------------------------------------------------------
1 - 1 -0.317 11.610 100.00 0 0.00 0.00 10000.00 1.000 1.000 0.000
1 - 2 0.057 15.753 13.53 7603857 0.36 0.13 4343.94 1.280 2.302 1.000
1 - 3 0.431 20.907 13.53 235503 2.06 4.25 1014.61 1.561 9.856 1.000
1 - 4 0.730 23.549 13.53 104045 3.10 9.61 759.58 1.673 13.165 1.000
1 - 5 1.047 27.353 13.53 68272 3.83 14.65 714.69 1.824 13.992 1.000
1 - 6 1.306 30.008 13.53 52798 4.35 18.94 689.52 1.921 14.503 1.000
1 - 7 1.567 32.906 13.53 44122 4.76 22.66 691.19 2.024 14.468 1.000
1 - 8 1.840 36.199 13.53 38723 5.08 25.83 712.31 2.144 14.039 1.000
1 - 9 2.058 38.524 13.53 35045 5.34 28.54 721.17 2.223 13.866 1.000
1 - 10 2.279 40.985 13.53 32344 5.56 30.92 737.09 2.307 13.567 1.000
1 - 11 2.510 43.681 13.53 30296 5.75 33.01 760.30 2.400 13.153 1.000
1 - 12 2.746 46.528 13.53 28701 5.90 34.84 788.24 2.500 12.687 1.000
1 - 13 2.973 49.241 13.53 27428 6.04 36.46 815.50 2.594 12.262 1.000
1 - 14 3.159 51.301 13.53 26376 6.16 37.91 833.16 2.663 12.002 1.000
1 - 15 3.352 53.517 13.53 25491 6.26 39.23 854.44 2.737 11.704 1.000


2) Hi-Lo + Side Count of 7's (5,000 million rounds)

 
play-all | rounds played = 100.00%
spread ev/h sd/h ror% n0 di score ekb avb unit kelly
------------------------------------------------------------------------------
1 - 1 -0.317 11.610 100.00 0 0.00 0.00 10000.00 1.000 1.000 0.000
1 - 2 0.065 15.789 13.53 5838267 0.41 0.17 3814.97 1.284 2.621 1.000
1 - 3 0.431 20.119 13.53 217631 2.14 4.59 938.59 1.517 10.654 1.000
1 - 4 0.763 23.695 13.53 96479 3.22 10.36 736.01 1.670 13.587 1.000
1 - 5 1.067 26.992 13.53 63972 3.95 15.63 682.71 1.800 14.648 1.000
1 - 6 1.349 30.041 13.53 49555 4.49 20.18 668.74 1.913 14.953 1.000
1 - 7 1.619 33.010 13.53 41552 4.91 24.07 672.89 2.021 14.861 1.000
1 - 8 1.863 35.603 13.53 36504 5.23 27.39 680.22 2.111 14.701 1.000
1 - 9 2.115 38.449 13.53 33046 5.50 30.26 698.94 2.211 14.307 1.000
1 - 10 2.345 40.977 13.53 30532 5.72 32.75 716.01 2.298 13.966 1.000
1 - 11 2.580 43.646 13.53 28628 5.91 34.93 738.46 2.390 13.542 1.000
1 - 12 2.793 46.001 13.53 27131 6.07 36.86 757.70 2.470 13.198 1.000
1 - 13 3.014 48.522 13.53 25924 6.21 38.57 781.25 2.556 12.800 1.000
1 - 14 3.233 51.043 13.53 24934 6.33 40.11 805.98 2.642 12.407 1.000
1 - 15 3.435 53.333 13.53 24105 6.44 41.49 828.03 2.720 12.077 1.000


If anyone is interested in more details like betting patterns or Wonging figures just let me know.

Sincerely,
Cacarulo