After posting the information on another "Leaping Serious 3NT," (see below), I happened to browse through the vugraph archives for the 2006 Reisinger. Strangely, I noticed that Moss-Ekeblad missed even slam on a hand where the Grand makes on a 4-3 spade split and the small slam is pretty icy. Their opponent bid the small slam with an auction I could not find.
Ekeblad opened 1♠ with ♠A109xx ♥KQ985 ♦A10 ♣x. Moss responded 1NT, presumably forcing, with ♠x ♥A10xxx ♦Kxx ♣A109x.
When Ekeblad rebid 2♥, this must have interested Moss, but he probably had no tools available to handle this hand. Enter the Leaping Serious 3NT!
After 3NT from Moss (heart support, great hand), Ekeblad should visualize that slam is probable and cuebid 4♣. Moss cuebids 4♦, and Ekeblad takes over. 4NT, RKCB, yields 5♥ (two keys, no trump Queen). If Ekeblad now realizes the potential of this hand and invites the Grand (5NT), Moss has enough to think about it. I like to think the Grand was at least sniffable.
So, if Moss-Ekeblad are a good indicator, this Leaping Serious 3NT might just be a good idea...