Sligthly off-topic, this aint specific for the Cell Master.... But here goes:
I found these recommendations from GP:
http://www.gpbatteries.com.hk/pic/300schR%20rev1.pdf
Seems to be on the safe side.... Charge rate: 0,5-1,0C (max 3 amps). I believe TCO is Temperature Cut Off, right? If so, they recommend to stop charging, when the batts reach 40-45 deg. C.
But they also seem to recommend using delta-temperature cut off. Why dont any charger offer that? That would work independant on varying ambient temperature...
And for those racing in the cold: Be aware, that GP only recommend fast charge, while the temperature is ABOVE 10 deg. celsius...