Today I tried my newly acquired prop guards on my P4P. The first thing I discovered that the obstacle avoidance system picks up the guards and will not allow me to fly forward or backward because it thinks it is going to collide. Simple cure, turn off obstacle avoidance. Not ideal but at least I can fly. Second thing I noticed is that (especially in a mild breeze) the AC appears very unstable, wiggling back and forth and not responding to the stick quickly. I tried immediately without the guards in the same breeze and found everything stable again.