new batteries will help, so will moving any other weight you can forward will help, are you running the cells in series or parrallel ? series obviously will yield more power.

your prop angle might also be a tad steep and the prop too deep and could be robbing you of speed, metal props dont flex so you will gain a bit of power there, id go for about a 40 - 42mm prop, something like a prather 215 or 220 or x440 should be a good starting point