I was just reminded of a strange little treatment.
Your partner opens 2NT. You start to transfer to hearts, when he suddenly super-accepts by bidding 4C. You have systemically agreed that 4D by you is now a re-transfer, either to sign off or to right-side the contract before you start asking for Aces. Makes sense.
However, a problem exists. The re-transfer takes away your ability to make a Last Train 4D call. Maybe you won't ever need on in this auction, but then maybe you will. What to do?
When a re-transfer is in play, you could use the straight bid of the suit, here 4H, as Last Train. The wrong-siding of the contract might not be as much of an issue when you are that close to slam anyway, of course.