Years ago, one of my favorite hands ever allowed me to post up the impossible.
I had a nice, balanced strong 1NT opening, and I opened 1NT accordingly.
LHO doubled as some sort of conventional something. Partner leaped to 4♦. She was an unusual lady, who thought Texas Transfers were too much to remember. Instead, she like 4♦ as an asking bid. OK. So, I answered 4NT, showing a maximum (4♥ would show a minimum; 4♠ a middlish hand).
She bid 5♦, asking for Aces. I dutifully showed my two Aces -- 5NT.
She bid 6♦, asking for Kings. I dutifully showed my two Kings -- 6NT.
She thought about this, and decided to bid 7♦. This troubled me. But, knowing her generally passive nature, I assumed that 7NT would make 17 tricks if she actually bid a grand in diamonds. So, I converted this to 7NT.
This was doubled with an echo heard a few blocks over. As it was matchpoints, I sent it back. 7NTX is not a contract at matchpoints. 7NTXX is.
When the opening lead hit, I realized that she forgot the system, or interpreted the double as changing things. Of course, few have seen a four-level preempt into a minor, when vulnerable mind you, after a strong 1NT opening from partner. But, here it was, apparently. This made 7NTXX not likely to succeed.
So, always one for the challenge of the game, I set forth on my task. Having reached 7NTXX intentionally (sure, the XX was on principle, but I "trusted partner" LOL), could I lose all 13 tricks? I cannot remember the layout, but I did succeed. -7600, somewhat legitimately.
All that said, the point is more practical. Do not forget to discuss the impact of competition and fall into the trap equivalence of doubling 4NT to force the opponents to remember if R0P1 or P0R1 is used.