A couple of months ago I wanted to start an upgrade process for my CS8, moving from MK electronics due to high BL temps flying in Colorado. I settled on the HoverFly Pro setup with Castle Ice 50 esc. The weather finally got a bit warmer yesterday and today so I started a series of test flights to really dial in the setup. I was getting little bumps in video, small jerks really, so I started playing with the main gain setting and adjusting the gains for the tilt/roll servos. I ran a full range from a gain of 50 to 110 for the primary gain (that's the primary way to adjust an HF board). Between flights, while charging I would review video from the FPV, Sony NEX7 and a Go-Pro I had aimed from boom 5 onto the back of the roll servo to see what was changing. Last pair of flights I started at the 110 setting and had moved the GoPro to the top of boom 1 facing forward to see if I could see any vibrations. Flew an out and back pattern that I was using for each flight. Landed and bumped the gain to 130 to see if things got any smoother. The result was at the end of the outbound portion I had a loss of control. The attached video shows this last flight, first from the GoPro, then the Sony followed by the FPV camera. The ship was nearly vertical doing a classic tail slide and struck on boom 5, driving that boom through the center section destroying my Dean's connector power distribution harness. I've sent the HF flight data log over to HF to see if they have any suggestions. Any thoughts or ideas as a post mortem appreciated. Things I have checked and my thoughts. 1. Battery was damaged but still showing 15.2 volts when I checked it afterwards. Sounds like there is power if I slow mo the GoPro until the ground strike. You will hear the LiPo alarm trigger, set at 14.4 volts. 2. HF boards checked ok postmortem. 3. Broken props on Booms 1, 4 and 5 were broken approximately 1 1/2 inches from the Hub.