We saw yesterday in a cost-benefit analysis the quad wins hands down for our current purposes and I overlooked the cost of speed-controllers. To power an octo with 22" props now costs $3300 at China prices, and for a quad at 26" or 27" it is $2500.
And whereas I planned to address each of the smaller U7s on the octo with its own battery, I've a larger pair of six-cell packs that I can gang together and feed all four motors of a quad from a single source. (They'd have to be wired in series in that case view of the fact the larger U11 motors for a quad run at 45v instead of 22v for the U7s).
An option at this stage is to use the existing three-foot frame with the U11s and larger propellers, subject to those front and back mounted topside and those left and right underside... in which event we can squeeze 26" props on the existing frame so as to provide the required 20kg of thrust. Alternatively we could run with top-side U11s if we enlarge the frame to one metre instead, though to do so we have to check the logistics of carrying it around.
Looking at the photo it clearly passes the 'Jimny' test at either size, and what it shows too is the practicality of adding a perimeter to the four-prong design patented back in 2014. In itself this neither sat flat in a car nor upright in a van, and its prongs poked people in the eye. Nor did it track normal to orientation, so the flight controller had to be mounted at an angle.
In fact if I've achieved anything to advance the cause, then it's that square.
"And the Oscar for Best Airframe goes to...".