I just noticed one flash, in which Ricky1016 mentioned, but i believe this would not be a deal to your spectators at all. I have not mastered this effect but I have been doing it many times already. I have to admit I also make the same mistake (turning the card over) but people hardly notice that at all.
I like Daniel's Version since you can sign on the card's face, half of the card's back and give it to the spectator as a souvenir. I've been using more visually stuning T&Rs before but most of them are uncheckable after the effect
