There is so much information available on the internet these days...with the inclination and mind set, anyone can do anything. If the roof skin is too thin and moves in the heat, after you cut the hole, frame it out on the inside, glueing the frame to the roof with something like Sikaflex. When you install the fan, use sikaflex under the joint, and screw through the aluminium into your frame. You can extend the frame with batons transversely across the roof to reduce roof flex more. No need to screw, just sikaflex on with some props underneath while it goes off. If I were local...I'd come and help. As I'm not. I'll pitch in where I can remotely!