There aren’t many card tricks for the parlour/stage magician. Maybe the hurdle is the lessened visibility of the card’s faces on stage. Tricks where the faces are not important, and the number of cards counts (as the Cards Across) are not affected by that.
Interesting is how one could produce an effect with freely selected cards the audience can fully understand.
I think the solution is in the framing and staging of the effect. If you stage the conditions by adding a few extra props which make everything clear to the audience, effects with a normal-sized deck will be comprehensible for the audience.
A perfect example is a trick that has long fascinated me, and which was published (along with solutions) by Ben Harris, years ago. I would consider this a modern card magic challenge, like Hofzinser’s classic unsolved card problems.
I developed two clean solutions, which I will eventually publish. But for now, stick with me with the description of the effect and observe how well this works because of the set-up.
On stage is a table. On this table are three wine glasses in a row. The performer exhibits three pieces of newspaper and forms them into cones. These are placed over the wine glasses.
Now a deck of cards is introduced, and three members of the audience chose a card each. The cards are signed and then replaced in the deck which is put back into the case and put aside. The performer announces that he will now make the three selections pass underneath the paper cones!
After the appropriate magical gestures (what are these?) the paper cones are lifted from the glasses and resting in the glasses are the three (signed) selections!
Now think about that for a moment, and please, don’t get disturbed by thinking of a method. At least, for now.
Think about the beautiful framing, set-up, and the way we prepare this miracle for the audience. There are three glasses. They are transparent, clean, and above suspicion. Most importantly, it displays them in an open position on stage, which can be appreciated from the back of the theatre. The situation is crystal clear.
Now three cones are made from innocent newspaper sheets. These are placed over the empty wine glasses. Again, the situation is as clear as possible, but, the conditions are impossible.
Because the glasses are empty and then covered with the cones, the audience will expect that something will happen to the glasses and cones. But even if they are at the back of the theatre, and maybe cannot see the details, this impossible situation is imprinted on their minds.
Later, when the revelations are done, they will see cards that have appeared in the former empty glasses. Maybe they only see white spots in these glasses, but somehow they will suspect that these are the chosen cards. And the magician proves these are the three chosen cards.
See how it is possible to enlarge an effect with playing cards to stage size?
Food for thought.