Sane Man, It's not your imagination> you will get a bit more wind blast on your head and shoulders with a double bubble when in an upright position, but you will get less on your body overall and far less when tucked down (which is what it's designed for).
By all means try the stock one again for experimental purposes, but I'm sure you won't keep it there long after having the double bubble.
How long have you had that screen on the bike? i would be very curious to know what you think of it's durability after few thousand miles of use.