Locking exposure on the 7D

As you've realized by now, spot metering only reads a very small portion of the scene, around 3% if memory serves me. And how many compositions have the point to be metered sitting right in the middle? Not many as we both know.

If you're going to insist on using this metering style you'll need to accept that it will require some extra work. I fully understand the value of this metering mode and use it mostly with extreme back lighting of a subject. My technique is to compose the scene and adjust the AF point, then recompose with the center AF point on the subject to be metered, press AE lock, recompose to my original composition, half shutter press to confirm AF, and then take the picture.

This requires a bit of work but the results are always metered correctly. With practice this technique can be accomplished in the matter of maybe 2 or 3 seconds.

I'm personally not overly impressed with the 7D evaluative metering and switched to center weighted metering a couple years back. When shooting high contrast scenes the 7D (at least mine) would consistently overexpose the image. I sent the camera back to Canon for a check up and the work order stated "camera was working within specifications" and that "metering was calibrated". When I read reviews here on DPR this tendency to overexpose high contrast scenes pops up on some of the best DSLR's around.