Runaway bidding

South	West	North	East
1	Pass	2	Pass
3NT	Pass	4	Pass
4NT	Pass	4	Pass
6NT	Pass	Pass	Pass

Last night Marya and Kathy went for a wild ride. Holding 20 points, balanced distribution, and four spade honors, Marya opened the bidding and then jumped, having determined that, with Kathy's heart support, a no-trump game was in order. But, especially given her unbalanced shape, Kathy took the jump as artificially forcing and asking for a new suit, which she named. Marya, more determined than ever to brake the bidding in no-trump, rebid 4 -- but 4NT is the cue for Blackwood, and Kathy dutifully counted her aces. A 5NT response from Marya would have continued the Blackwood and the fugitive auction, so she leapt to 6NT and heroically brought the auction to an end with a resounding slam! After that, scoring 12 tricks was easy. Would you have bid it differently?