"You can look at the 6s flip fpv thread on rcgroups. I know that you state 4s, but according to the thread, its fast, nimble, and gets 12-18 min of flight time. I believe it might be a 400 size though.
"I know this might be a odd ball request, but is it possible to make a vtol with the pixhawk? Iam probably the only one thinking this might be great for that."