I have been poking this build with a stick occasionally as I was working on my Power Wheels Rover project in the meantime. But now I am back to working on this quad.
I have had a hard time getting this thing to play nice, and last night while reading more about ESC timing I realized that may have been my problem. I was having occasional motor spurts, and sometimes one or two motors wouldn't spin up initially, they would pulse and behave strangely. Early this morning I set the timing on the ESCs to low, and unsurprisingly it fixed the issues I was having.
I did a full config reset running 2.8.1, with motor size set for medium (0.110). Flight is a LOT more stable than it has ever been, and had a slight breeze too. All is left for me is to get more flight time, and practice, practice, practice!
More photos etc at: http://projectable.me/post/35643555854/more-tweaks-to-the-qav500-pl...