TOPIC:

Today, Astonished, seen how well a Dual Battery Setup fits in a Kyosho Ultima Lamborghini and decided (Almost) to try it, II think this, coupled with an ESP could triple the runtime of the car, also, allowing me some decent running time out of my dieing el-cheapo NiMh's

My dad did it on the clod buster (3packs). And on an old off shore boat. That works fine. Just do it

Ouch too late I remember that I had a pesky sanwa rx on the ultima... hate those things... (the ESP I was planning to use is Futaba 2.4ghz compatible while the ultima has an old sanwa 27mhz rx from RMS Titanic era) I can mate them?

Yes. Because you are working on the running time not on the voltage.

My doubt lies on the wiring order...

Parallele. + with + and - with -. parallele = Amperage and serial = voltage.