4.8v are just fine, but with a 6v pack you can lose a cell in flight and not lose the plane. As long as the battery has a 1500 - 2000 mAh rating you should be able you fly most of the day with out worry..... ALWAYS check the pack with a loaded meter before and after each flight to keep a close eye on your battery's health.

I just bought 4 of the "Tenergy" 6v 2300mAh packs from all-battery for a few larger planes and so far I am pleased with the quality.... This weekend I am going to run a few cycles to see what the true capacity is and if it matches the rating on the pack. So far I have only done the first slow c-h-a-r-ge for conditioning, and they have held the c-h-a-r-ge, as they should, for a week now. The packs seem very well assembled and came in the typical partial c-h-a-r-ged state.


Edit: for some reason the word C-H-A-R-G-E is no longer alowed on RCU [&:]