Match points, your agressive bidding gets a good dummy reward.
LHO leads ♥5. And lets say you try low from dummy and capture RHO's ♥J with your queen.
a low spade is led to the king, and RHO drops ♠10 under it.
Now say you call for ♣10 from dummy and RHO plays ♣J and you win.
Now if you could just test if ♣J is singleton it could be a big inference about how the spades lie. But it doesn't seem very easy to do so without jamming your comunications. Any ideas?