Hey Mike, Gary in Nashville, I would say a safe bet is your correct I would not drill through the PCB and risk the chance of bridging two different traces on the board. It appears that DJI just silk screens black paint over their circuit boards to hide the traces. The bottom of the board is easier to see where the traces are but on top it's nearly impossible. A second option may be to use something like shoe Goop to mount whatever you want to mount. It dries fairly fast, won't harm electric connections, is flexible and will last a very long time. I had the same thoughts as you since I was thinking about mounting some vibration isolation dampers to the bottom of the board and hang my GoPro camera on it to remove the vibrations. I think the solution is to use zip ties loosely connected as there are large holes on the bottom plate on the 450 Naza frame. Good luck on whatever you come up with!
Gary