Wrong contract isn't always a disaster

I haven't had much interesting hands lately. This is the only interesting one, where we ended up in the wrong contract:

Dealer: North Vul: Both Scoring: imps	♠ T875 ♥ 654 ♦ A82 ♣ A43
♠ KQ643 ♥ KJ93 ♦ T ♣ QT6		♠ J92 ♥ AQ82 ♦ 43 ♣ 9852
	♠ A ♥ T7 ♦ KQJ9765 ♣ KJ7

The auction went:
pass - pass - 1♦ - Dbl
pass - 1♥ - 3♦ - pass
3♥ - pass - 4♦ - pass
5♦ - all pass

I considered a 3♦ opening immediately since partner passed, but the hand was just too strong. On the next round, since partner passed (no RDbl), it was probably best to jump in ♦ for several reasons. Now partner came in action and later regretted he asked for a ♥ stopper instead of hoping for a 4-4 ♥ split. 3NT is laydown, 5♦ can be defeated. Anyway, after trick 2 I knew I was pretty safe.

LHO started with a ♥ to his partner's Ace. He made the wrong choice. Think about it: what is the best continuation and why?

He switched to a small ♠, after which it was pretty easy to squeeze LHO in ♠ and ♣. Thanks to the Double and the lead I knew RHO had some values left in ♥, so the ♣ finesse would not work.
A ♣ switch can ruin my communications for a squeeze later on, but I wonder how he could know to switch ♣ and not ♠. Even if he plays a ♣ now, he needs to overtake ♥J and return another ♣ in the next trick.

So I took ♠A and played my last ♥, rectifying the count. LHO took his J (which held) and tried ♠K which I ruffed. I only needed to ruff 2 ♠s to set up ♠T as a menace, to combine with my extended ♣ menace, ♣A and ♣K taking care of the communication. ♣K is not necessary, but the Ace is vital.

After ruffing one more ♠ and running ♦s, LHO got trouble. He had to keep ♠Q and ♣QTx. He tried the ♣, but that didn't help, the hand was an open book. ♣A, followed ♣K pinned the Q and 5♦=.

As you can see, I don't need ♣K in the end game because it's a positional squeeze: if LHO discards a ♣ my ♠T is high, otherwise I discard ♠ and pin the ♣Q.