I fly a L-19 alot nowadays, We use them for banners. I use about 15 degrees (first notch) of flaps to help get better climb. We also have the bigger 0470 in there. But on a hot day with a big billboard at sea level they dont like to climb. I can imagine how it would fly up high. I wonder if they had any flaps out? Also form the video it looks like he flipped over after hitting the first treetop.