I think this has been a really interesting thread. The project is ambitious no doubt, and the OP may possibly be over his head, but he's working with a professor and (I'm assuming) a competent team who will take the necessary precautions to avoid legal and safety issues. If the project fails, it will still be a learning experience for him. So let's be helpful, ok?

A thought that hasn't come up here but I've seen in other discussions on similar design goals is to use a rocket or a balloon to get up to altitude. Have you considered this? It would allow you to drastically reduce your power system to save some weight and have longer loiter times at altitude. Sure, it doesn't replicate what one would see in a full scale plane but if this is intended to just be a useful research vehicle that shouldn't matter. I could definitely see a successful design where a balloon takes the plane up to 5k feet or however far you want to go, then is released as the plane's prop starts the cruise. Of if you really want to fly up to altitude or be better in the wind, a rocket system that can be jettisoned when it's used up gives you some free altitude.