Truing up the Running Count
I play shoe games almost exclusively and true up my count to the "count per 2 decks" rather than per deck or half deck. It's not necessary however to divide by how many double decks remain, but to simply use a predetermined multiplier.
There are a couple of benefits to this method, the main one being that your running count and true count will be nearly the same as you approach the shuffle. Another benefit is that all your indices double in raw value, resulting in less truncating/rounding and therefore greater accuracy.
Examples: Off the top of a six deck shoe, the multiplier is one third the RC. With one deck gone, multiply by .4. With two decks in the discard tray, multiply by .5. 2.5 decks in, multiply by .6. Three decks equals two thirds. 3.5 decks in the discard tray equals .8. At the critical stage where four decks are gone, the running count IS the true count. If you get as far as having 4.5 decks in the discard tray, multiply by one and a third.