Quoted from classicgamefan:Just FYI - The score doubling only comes into play if you get a Mystery Select with a score less than 100M or a Super Mystery Select with less than 300M. I think it's also possible with a ???, but the score limit is based on whether or not you recently got a SMS or not.
Jon
Thanks for the info! I suspected something like this, since the double score award usually came up early in the game.