Heres a little project some of the younger players may consider. I worked on this 20 years ago. Dividing by decks or half decks is always mentally taxing. Playing heads up going into the 40th round your looking at about 100 cards left and dividing by 3.69, 3.48, 3.28 etc. in HI-LO it would be half this value. If one could keep track of sets of multipliers it would take a kink out of the mental gymnastics. Its easy for the first 10 rounds (1 deck approx.) just using .09 and .1. The second deck .11, .12 and .13. 3rd .14.15.16. Make the excel spreadsheet if you like the idea. Getting into that critical 5th deck you have .27.29.31 as your multiplier for the 40,41,42 rounds. I don't know how some of these guys can do these side counts I am not that good but to develop a routine of thinking of decks as sets of ten rounds in the heads up game it would not take long to lock down these multipliers in your head and free up some valuable disk space. Just my opinion, I could be wrong.