Well I finally pushed it too far and lost my quad! I was experimenting with missions and discovered the hard way that each waypoint if you are in relative altitude mode will cause a climb at each fix if the altitude value is not zero. Suffice to say that it climbed pretty high by the 3rd waypoint and was drifting off point (perhaps wind but it was very calm as the surface but I was quite a bit higher than I had planned) .
This is a 120mm quad so pretty hard to see. With my previous missions I had only 1 real waypoint so my poor flightplanning in regards to altitude was not evident.
I knew something was wrong and had set a home position just for that reason- I selected return to home. It attempted to turn and fly back but lost control in the descent (contributing may be I had recently increased the max auto descent to 3 m/s from 1.5 m/s). I could see it looping and flashing in the sun as it went crazy. I tried to control it in manual mode but it was too late (I did hear the motors so it hadn't lost battery power). I just killed the motors so at least it wouldnt fly into the ground at full thrust.
So it dissappeared behind some trees about 80 meters away. No idea where it is...
Things I will do differently in the future-
-test my max descent rate after changing it
-obviously not increasing relative altitude at each waypoint
-do these mission experiments in a more open space
I wish there was a tool to "fly" through your mission and or a 3 dimensional view of the mission rather than viewing the waypoints on a 2d map. Maybe since I won't be flying for a little bit I will give that some work within the android app.