First, one has to ask, how do you get to the six level without even mentioning a 5-4 major suit? Oh, yes, the negative double did imply spades. But given that the North player could probably survive in a spade contract opposite three small spades and that South isn't likely to introduce a suit where he has three small, though yes, I know it has been done, I would question the wisdom of the negative double. There are a couple of other reasons, aside from the sheer disparity in power between the two suits indicated, why I'd eschew that neg double: The leap in hearts indicates that on my next turn, the bidding may be up a couple levels, and further, I think the hand is strong enough for two bids anyway, and though I usually enjoy the pleasure of bidding two or three suits in one whack, here's a case where I'd feel more comfortable getting that powerful major in first and then bidding diamonds if circumstances warranted.
And then North would surely have played the hand better. Or would he have locked himself in trying to take care of diamonds in the (then) closed hand and fail to see how easy the hand would be in a dummy reversal. In any event, this declarer went down in six clubs, and for the life of me I couldn't pick out why for a few minutes. This was partly because a few of the cards were obscured in my printout, and also the record went out only to trick 9, for I'd used too large a font and the next four tricks were lost. And then I pieced it out.
Declarer has two ways of transforming that four of hearts into a winning trick, of course. First is that he could simply ruff it before finishing the drawing of trump. Surely he wasn't fearful of an overruff with only 3 hearts and indeed a raise by East. And then the other way, of course, is to pitch that lone heart on the long spade, though that gives up an obvious overtrick he could have by ruffing the heart and pitching the diamond. Do I suggest that declarer did neither and went down! Yes, indeedy.
Opening lead the three of spades, won in dummy as declarer pitched his lowest spade from the closed hand. Naturally. Now three trump tricks, then a top spade, again declarer's lowest spade being pitched, a top spade, and then the fourth round of spades won in the closed hand, of course. Declarer led a diamond at this point, but even if the A had been onsides, it wouldn't have helped him much. The failure to unblock is all the more egregious in that the 8 and 7 were just as capable of winning the fourth round as the 9 or 10. It wasn't quite as if dummy showed A K Q 6 2. There, indeed, you'd want to hold off unblocking one round in case West holds 'em all, allowing you a marked finesse against the J. And if the suit wasn't splitting 4-0, then you'd want to make sure the 6 would win the fourth round. Period. On a 5-4 fit, without outside entries, you want the 5-card holding to win the fourth round. Which is to say the 8 or 7 must win the fourth round.
Six clubs doubled? Even without an overtrick, that beats six spades. But East said, "Oh, you poor fish in an inferior contract. I'll give you an opportunity for a top board." And declarer replied (in essence), "Oh, no, I'll have none of that."