Frame for a 31mm "Tinywhoop" style drone with a 25mm AIO board (the board in the examples is the EMAX Nanohawk AIO).

The major issue with this design is flexion of the "X" base affecting trim. Print it with as stiff a material as possible -- I would recommend avoiding flexible materials like PETG or ABS. It of course can break but, given its low mass, it's harder than you might think if you avoid aggressive flying. The other problem is positioning of the battery, which has a significant effect on trim as well if you are not consistent.

To assemble: print the "X" base and screw down the motors and flight controller, the latter using "gummy" vibration dampeners. FC screws are 2mm, motor screws are 1.5mm as typical of 1S motors. The top will then snap fit. Put the camera mount onto the top rail, then snap the camera (tested with Caddx Ant) into the bracket -- the mount will flex slightly to secure itself to the rail. I use rubber bands to hold the battery in place, see picture.

There are two stands for leveling and pre-arm stabilization. I prefer the larger one but both work.  The example photo of the assembled frame shows it on the "small" stand (red).