How good a passed hand?

Had this hand yesterday playing IMPS that my partner and I screwed up. I was in 3rd seat, no one vul, and picked up AJ4 J72 A KQT862. It went P - P to me and I opened 1C, P, 1S by pard, P. I liked my hand, but dont like to get to overboard when I don't know where we are going to play the hand, so bid 2C. This went P 3C by pard, P back to me.

This now makes my hand very good. Pard not only was able to take another call, but raised clubs. I decided to show my Spade support with 3S now and it went P - 4C - P back to me. So partner likely has 4 not too great Spades, since did not bid 4S, and at least 4 Clubs, with probably 8-10 HCP in hand is first estimate.

I have 5 1/2 loosers so need partner to have 3 cover cards to make 5C a reasonable shot. If I give her the A of Clubs and the K of Spades, I still need a Heart card for 5C, or Heart shortness with Club length. I finally decided that was a lot to ask from a passed hand that could only bid 4C on this auction and since we were not vul, I passed, not without some trepidation.

LHO led the A of Hearts and partner put down a most unexpected dummy, K873 -- T974 AJ754. Of course my decision to pass 4C was very wrong, when the Spade hook was on I made all 13 tricks. But I also think partner must take a stronger action over my 3S. When I rebid Clubs, then made a forward going move supporting Spades over 3C, her hand became an absolute gold mine. I think the 2 bids available over 3S should be 5C or my personal favourite, 4H. It turns out that if she bids 4H, that is such a great bid for my hand, there is a good chance we may get to the slam now. The problem with 4C is it can be made on so much worse of a hand, that it does not convey the playing strength of that hand once the double fit is found.

We wound up loosing 6 IMPS on the board, but had a chance for at least a push if not a nice pickup, when the opps played it in 5C. I think people are still under valuing the power of a double fit. When you find that you have 1 in an auction, I think you can usually count on a full extra trick from the hand, provided you play in the correct suit, the 1 that splits between you evenly, most times :)