If it helps, I run 2 3000mah 30c 4s blue sky lipos in parallel all the time. I charge them with a parallel balance plug and always leave them connected in parallel. I've never had a problem with them, the cells stay balanced pretty close between each pack.
It probably helped that these packs were purchased at the same time and likely came from the same batch, and have never been apart. The cells have always been pretty much a mirror copy of each other.
I've read that running packs in parallel that have different amounts of usage is not always the best way to do it. I would suggest buying 2 cheap batteries and try it out. Leave them connected all the time. Just turn them into a 4s2p suggested earlier.