The number one thing with HV's is getting them hot on the charge. To achieve this you must use a peak detect /voltage thresh hold that is higher than other NiMH's.
On the Millenium I would use 72 mv for the entire pack which equals 12mv per cell.
We have found that higher charge rates give a bit more power.
We have alo been traying our HV's. This keeps the voltage up and the packs are more consistant. It will remove some runtime so if runtime is a major concern don't tray them.