Hi mate! I dont think its not an option we had over here, if its was open it would let all of the water falling from the sky in lol! I can imagine that it would be heavier with it being glass and the electrics for opening etc. Its not going to be a massive difference to handling on the road though, it depends how seriously you take it. If you are going to spend every weekend shaving tenths off lap times then I wouldn't bother but I dont think that is the case.
Get it and enjoy the sun you lucky so and so... :thumbup: