Yeah, wingrock as you describe is pretty common really. I am setting up a 3D Foamy Raven (Depron, Pro kit) powered by an AXI 2212/34, and decided on the Apogee 830 3s1p packs, I bought three of those instead of two 1050s. My run time estimates were around 10 minutes (over actually) based on my flying style with the 830s and 12 minutes with the 1050s. . . and a weight savings of .42 oz which I figured I needed more than those extra 2 minutes between battery swaps. Long run times are nice. . .but if it's 3D your after then so is a low wingloading.

Given what your all up weight is I that battery may solve the issue, its giving you a little heavier than ideal 3D wingloading.