So what does a cat toy and a PCB have to do with UAVs?
Very easy: One of my dogs had taken my cat's pole toy and left little but the handle stick. I was wondering what to do with that now. At that time, my MF450 frame was on my desk waiting to be completed and I shortly before read about external LED indicators. I also mounted my APM on top of the frame and was worried about damages in case of a flipover.
So - I cut the stick in halves - well somewhat half... Then I soldered suitable resistors for 5V to the LEDs and short cables with 3p jumper plugs. After that I filled the respective parts of the stick with heat glue - pretty much completely to give some additional stability. For mounting, I pushed an M3x35 bolt into the still soft heat glue.
As a result, I have two little masts which carry the external LEDs for GPS and ARM as well as double as some kind of "roll cage" to protect the APM in case of a crash.
As for the PCBs, I did have massive stability problems with my quad in Alt Holt mode and was advised that vibrations might be the cause. The MF450's gimbal comes with rubber balls which are a good bit too soft for that gimbal construction (the gimbal shakes badly) so I mounted the roll servo to the frame with double-sided tape and had the rubber balls as a leftover. I also recently bought a 50 pack of small PCBs from eBay, so I made a quick-and-dirty (and cheap) anti-vibration mount from 4 rubber balls and 2 PCBs.
That's the final result:
The anti-vibration mount will be tested soon after I got my new props.