I have some 8x16 motors. A few came out of a Syma, then some of another geared quad that someone brought me. I was not so impressed with performance.
7.0x20 motors and 8.0x20mm motors were already close enough together in performance, so I didnt see the need to add another step to the portfolio at this point.
Also, the use in RTF quads is so limited that I dont expect much demand from people wanting to fix these quads, especially since you usually can modify the motor mounts and fit 8x20mm motors.
Adding a new motor to the list will cost me one or two days of work and a few thousand dollars initial investment.
It’s a bit hard to justify right now, but if I manage to sneak in a small sample batch, I will let you know here.
What I am considering though, is a 7x16 variant with 1mm shaft