I thought that the idea of these diode/resistor circuits was to balance the cells and the discharging was done by your R/C car. Battery conditioners are different, they cycle the batteries by charging and discharging them repeatedly.
For the resistors, I would start at around 25Ω (20mA). My logic for choosing this value is that the cells should be discharged (after use) to around 10% of their capacity and 20mA will mean they will be balanced the next day.
BTW, in your simulation, gradually reduce the cell voltage and see at what voltage the current becomes negligible. It should be around 0.5V.
Mike.