Sorry to say but you can't do what you're saying. The EVX2 esc has 2 battery inputs, each of which are meant for 2s. The esc then makes a series connection out of these 2 inputs inside the esc. One of these inputs can take 3s, the other input powers the bec and can only take 2s. So you can run 5s through the EVX2 but it has to be in the form of a 2s pack and a 3s pack, you cannot connect a 5s pack to the esc through either of the inputs.

I'd also like to offer a word of caution against running packs in parallel. The idea sounds great, double the mah for lots more runtime. But in reality you're adding a bunch of weight to the vehicle hurting performance and increasing strain on components while running and also in the event of a crash. Plus you still have to charge 10,000mah, whether it's 2 packs or one it's still going to take the same amount of time to charge 10,000mah.

My biggest opposition to parallel packs comes from having to connect them together though. Let say you put a Castle MMM (it has brushed mode) in there with a parallel harness and want to run a pair of 5s packs. When you connect the 2nd pack there is no resistance between the two packs. If the voltages are not equal one pack will be rapidly discharging while the other is rapidly charged until the voltages are equal. We know lipos don't like being charged or discharged too fast and the more of difference there is in pack voltage the more they're not going to like it. Then there's the fact that one pack is always going to be stronger than the other putting more strain on it. I've had a few packs that were made up of parallel cells (2s2p) and it never worked out well. One of the parallel cells would always drop out before the other way quicker than a comparable non 2p pack.

Just my opinion on the subject.