Partner can't have the heart A....opener would then have bid 2N on an Aceless 12 count.
Partner shouldn't have the club Q, unless he has a very unlucky Q987.
Partner should hold one but not both of the heart K or the club Queen
Partner might well have a stiff diamond, and be unable to smith.
It would be very unlucky for him to hold Q987 in clubs AND be unable to smith. So I will pay to that combination. I will assume that partner has twice told us that he doesn't like clubs.
Moreover, when he holds Q987 in clubs and a stiff diamond, maybe he has 5 hearts, such that a heart switch doesn't cost anything
So it seems to me that the heart switch loses immediately only to something like Qx AKx Jxxxx Kxx, where the heart J becomes the 9th trick, whether we lead low or the Q.
I have ignored partner holding 987xx in clubs....I don't think the 7 is the right card there, and partner can make up for this by discouraging in hearts with Kxx(x) and encouraging only with K10x(x).
If we are switching to hearts, and I am, I think the Queen is the best card. I hope partner has the 10
'one of the great markers of the advance of human kindness is the howls you will hear from the Men of God' Johann Hari