A much more practical size! The previous version would have dwarfed most featherweights. Looks like you have a well planned, measured approach to building. Looking good!

As for the batteries, you'll easily run one battle, probably two, maybe even three with 4.6ah. Tormenta 1 had five 12v drills (overvolted to 18v) with a total of 5ah batteries. We charged once across Friday, Saturday and Sunday at the champs (7 battles total), and we only actually put 1ah back in. We still have loads of capacity left even now, having run all sorts of tests with the batteries since then.

Point being, 4.6ah will be ample (lol). If you have the weight, though, you may want to run both batteries. Putting them in parallel would mean you'd only have to charge once in a blue moon, but not only that you'd have double the discharge rate available. I don't know what those motors pull at stall, but it's likely to be near 15a or maybe more. Those NiMH packs are rated to around 30a I believe. Slamming drive on from a standing start might blip the demand beyond a single battery's abilities. Having two batteries could potentially improve drive power.

Then again, truth is, a single battery would be perfectly good, I'm just blabbering.

Keep it up!