Ok, we have updates.
I got the cutting deck built and installed. Also installed the motors, esc's, and the cutting heads.
The wiring harness is complete. It even works.
The 3rd channel on the radio does successfully turn on and off the cutting deck.
It's still untested, but that will be coming soon.
It appears like housing 20,000mah of Lipo on 4S will be pretty easy.
Here's some pictures.