I have to strongly disagree here. If I read this correctly, Martin, you are saying to position the cleat/plate so your heel is skewed outward. Well, everyone's feet are different. Some folks feet are straight like this --- "| |", others are pigeon-toed like this --- "/ \", and others are slew-footed like this --- "\ /". If you try and adjust the cleat off-center in a way that is not natural to your normal foot-alignment, you are asking for problems later down the road. If your cleats are not aligned properly you will end up with tendonitis around the knee joint.

The following works for me:

Hop on a stationary bike that's set up with your pedals. It's also convenient to have an assistant to help you later to mark the position of the cleat. Position the cleat fore-and-aft so the ball of your foot is positioned directly over the pedal spindle. Tighten the cleat so it doesn't move backward or forward but allows you to move your heel in and out. (I use the Look-style cleat with 3-bolt pattern, so this isn?t difficult. I don't know if this is easy with Shimano pedals, tho'.) Get on the stationary bike and spin for at least 5 or more minutes and your legs will gravitate to the position that is most natural to them. Get your assistant to mark the cleat position before removing them from the pedals. Get off the bike and tighten the cleats in the position that was marked. Get back on the bike and spin again and make sure it still feels comfortable.