I would think that given it is on the roof, it would be much less secure than anywhere else. i.e. The 'sniff test' is thermal cameras that monitor via helicopter (air). No thermal footprint, but I don't know about you, when you look at a roof, usually you don't expect to see anything on it. Therefore if something is on it, it may attract a great deal of attention, to onlookers, air traffic, or otherwise. Plus if you have a puff when you take care of your plants (which I happen to do every time), it is only a matter of time until TUMBLE