The 3DR Web Assembly manual shows the rear ESCs stacked together. I emailed their tech support and their reply was that it is OK to do so. Now, if I can only figure out where to put all the wires. Oh yea, the PM is still hanging out. Trying to get ready for Compass MOT setup step, once this is all ready.
I am assembling the 3DR Y6 Kit with all 3DR electronics and APM 2.6.
3DR Web Assembly Manual photo:
My "under construction" photo: