This is my 7-inch version of TBS Source One quadcopter frame. So far, so good, Source One is really tough and stiff frame so all the problems with resonance and oscillations in flight should be over. And looks like they are over.

It might sound like a good old V8 engine but flies smooth. And after all, that was my ultimate goal. So let's say "bye, bye" to wobbly-wobbly iFlight XL7 v2 and say "hello" to 7-inch Source One! 6mm thick arms are the way to go!