Loving the build so far! Oh and for control a Sabertooth is great for mixing, but as far as I know the 2x5 and 2x12 only support two channel mixing. Since adding a mix in the TX will be tricky, I would suggest putting the two channels on a mix to control with one stick and the other stick for front steering. I think this would give the most control but of course you would have to sacrifice something else. What are you using to drive this? There might be an easy way to trick the motherboard actually. If you are running without a control board you might have a bit of difficulty mixing channels.