Switched my gecko to DJI FPV; the Air Unit barely fits under the belly if you split your FC + 4in1 ESC to use both 20x20 bottom slots.
I used the sticker foam left over from building the frame and stuck it on the top of the air unit to make sure it stays in there, the unit does not move at all.

I am trying to get it under 250g which is possible with a GNB 520mah batteries but flight time is ridiculous.
Best suited for this build might be the GNB 550mah HV 6s, or the GNB 700mah 4s SHV.