Does not everyone agree that it is a basic tenet of bridge to describe YOUR hand as best as possible? If an opening 3nt means a solid 7 or 8 card suit, with not more than an outside Q, is that not the fastest and best description of this hand? Is there any reason why partner, although a passed hand, cannot have the two round aces and qx of spades making 3nt cold? And if 3nt looks wrong p, of course, pulls to 4c and u correct to d. And does not this bid also allow p to sac if it is right, knowing almost exactly what you have? In sum, if you play the convention, I can see absolutely no downside to using it and plenty of upside.