I wouldn't do it I don't think......not because of the voltage, because crossman is correct, voltage in parallel is the same...but because of the condition of the individual cells. Which you wouldn't know......now be careful using rechargable batteries instead of regular AA batteries which are rated at 1.5 V a cell.....rechargable batteries are rated at 1.2V a cell....
So to make 2 packs...each pack's cells wired in series (voltage additive)(current the same) then each pack in parallel (voltage the same and current additive) on a 4 cell pack using regular AA's you have 6.0V on a 4 cell recharable pack you're at 4.8V