Regarding that 6NT hand posted above, let me be provocative: When partner leads the heart K you can deduce that he has the club Q (or better). Why?
If pard has the heart A to go with the heart K (of course he doesn't after the Gerber sequence0 then he will of course cash it at T2. So: Declarer, together with dummy, has the spade A, the heart A, six diamond tricks (assuming he holds at least two Ds in his hand the suit will run). That's 1+1+6=8 tricks. If declarer has the club AKQ, even if it is AKQ tight, you have three clubs and the board has four so pard has at most 3. Declarer will, sooner or later, cash the AKQ and the 8 on the board will be good.
Thus: Unless pard has the club Q or better, the hand is over. So, for the purpose of planning the play, he has it.
There is another inference after declarer ducks the heart. If declarer held AJT he presumably would have taken the A at T1 and led the J to establish the T. So pard's heart holding is KQT or possibly KQJ.
I assume from you play of the H7 at T1 and spade 3 at T2 you are playing udca. Thus pard knows that you do not have the heart J and you do have something in spades. Even in the virtually impossible on the bidding event that he has the spade K as well as the heart KQ and the club Q, he can now comfortably toss the spade K, keeping his heart and club threats.
When declarer played the heart 8 from the board, I think covering with the 9 was an error. Surely pard has the Q so declarer is not about to let the 8 ride. And there is a downside. Presumably pard took the heart 7 at T1 as denying the heart J, but when you cover the 8 he has to worry that maybe, just maybe, the 7 was an encouraging card from J97. Declarer might have started with five hearts. Pard will be subjected to a pseudo-squeeze and you don't want him even thinking of pitching the heart Q on the assumptions/hope you have the J. Of course this gets clarified as you pitch more hearts on the run of the Ds, so it really shouldn't matter.
As long as the spade 3 at T2 showed values in spades, pard can pitch all of his spades on the Ds and then choose between a club or heart after he sees what declarer does. but this is true only if he is confident that declarer holds the heart J Declarer comes down to the heart J and the AK (only) of clubs so it is safe to toss a club.
It's a hand with possibilities. Declarer might take the A at T1 and try a pseudo without the count.
Added: Seems it makes 6D.