Ah, that sounds familiar. A wooden shed I have occasionally used in the past does that too. Everytime you go there you have to spend time clearing webs from the lights and mains sockets.
It was the dryness of that which made me wonder why I put up with the POD’s condensation problem.
I’m thinking 7ftx7ft with a pier mounted NEQ6 and probably a Celestron 11″ RASA (can’t afford a 14″ RASA and mount upgrade) plus something like an SX694 CCD. Am not sure 7ft is big enough, but am not keen to throw away garden – the run off frame area is pretty much dead space in the garden. Also , I want to keep the thing as low profile as possible so it doesnt take over the view from the house – yeah, I’m not making life easy for myself.