I have used the Powerlab 8 with MPA board. I have tried 6, 4 and 2 5s packs in parallel. Sometimes the packs would charge and balance well while at other times the packs would be badly out of balance. I even got a second MPA but that made no difference. I have tried Zippy and Dualsky packs and both produce the same random unbalanced result. I would get packs coming off the charger at 99% with others at say 86%. The low pack would have one low cell and it would take several hours to rebalance the pack. I have parallel charged 6s packs with no problem so I'm not sure why I had problems with the 5s. Maybe it is just a matter of averages. One cell of a 5s is 20% while it is 16.6% for a 6 cell. So the 6s packs may not have been that well balance either but a low cell is not contributing as much the overall final voltage and I have probably willing to accept a pack at 96% of the charger. While in theory parallel charging should work in practice it doesn't seem to. I now have a iCharger 4010 Duo and a 3010B. Both are great chargers and I can charge three 10s packs at once without having to worry about unbalanced packs. I would stay away from parallel charging and stick to series charging.