Wanted to install the DJI system also to my Mr. Steele Apex, because I like this Apex frame a lot and love the DJI system!
Designed a special air unit/antenna mount to keep the air unit in place. I had to use 20 x 20 stack to fit everything in.
With these parts, it is really easy to convert the Apex frame to fit the DJI.
Came out pretty simple and nice? :)

All tpu parts available here: https://www.thingiverse.com/thing:3995506