Here's the thing, this gimmick is very cool. It's very clever and pretty easy to use.
The
bad thing is, the spectator cannot look directly at the card at any time without the card being
switch out first. That's BOTH sides of the card that cannot be directly viewed by the spectator
without somehow obscuring their vision with movement or lighting. This is no way a practical effect
for a strolling magician. Fine for camera.
Also my gimmick broke in 10 mins. Materials are
given to fix it, but it is quite precise and i really can't be bother fixing it as I'm never going
to use this trick at a show.