I built this one up specifically for the DJI O3 system I got for Christmas. Fun little build! It's probably a bit on the heavier side for the 3mm arms on this frame with 1607 motors and 1300mAh 4S, but without an HD camera it still rips pretty well! This was pretty much an experiment to see if I can get 5" type performance in the 4" without the GoPro. So far it seems to be working pretty well, though I've already found it doesn't have the wind penetration that the heavier 5" has. Still dialing things in and the tune needs work, but I'm excited about the possibilities the O3 brings.
I'm also giving a try with AM32 on this build. Pete (Alka) Sent me this T-Motor esc with AM32 preflashed a while ago and I did some testing on the bench, but I'm finally throwing it in a drone with the latest AM32 code. So far I'm pleased, but needs some more time to draw any significant conclusions. I love the potential in open source 32-bit firmware, and Pete has done some great work here, so I'm very optimistic for the future of AM32.
Photos
Any problems with not soft mounting the O3? I built the same frame with my O3 and had to make some TPU mounts.
Nope, none at all. As long as you're not trying to use stabilization there should be no problems regardless of how it's mounted. As far as I know the issues only show up when you try to use EIS.