Thanks for the thought and potential pitfall. I am going to use a purpose designed socket. I have quite a lot of experience in cutting metals of all types and thickness (I spent many years in the electrical control panel trade) so I'm not anticipating problems from fitting the socket. I have already considered that I might need to use strenghtening to support the socket for when I'm plugging/unplugging, the only problem I might have is due to being unable to remove the internal lining. I might have to be 'clever' and fix some strengthening from the ouside before fixing the socket, maybe using plywood or aluminium angle strip, possibly using filler to fill any gaps caused by the curvature of the panel. I'll let you know how it went and what I used once I've fitted it.