SPD cleats destroying shoes

I've got a pair of Shimano shoes which have had the SPD mounting area worn away by cleats which have loosened or dug into the plastic and worn the plastic away so now it is almost impossible to get the cleat to position correctly without it twisting and sitting in one of the newly formed grooves in the sole. Is there a way to avoid this? Should I be using a washer of some sort between cleat and shoe sole?

Washers might do the trick. My M183s do show wear, but I guess the fact they have not been slipping has saved the mounting area.

I overcame this by putting the cleat in the position I wanted and tightening the fuck out of it while holding it there, creating a new slot for it to sit in.

I tried tightening the fuck out of it but that forces the cleat to follow the path of least resistance straight down into a rut.

Use something like this in between the shoe and cleat?:
http://www.chainreactioncycles.com/Models.aspx?ModelID=25138

Although I don't think I would want to pay £9 for a bit of steel with a few holes cut in it, so maybe make some yourself.

Isn't this why they come with those plastic shims?

I don't recall a plastic shim. Got a photo?

Those crank Bros. washers look to be a good bet. Something SPD specific would be nice though.

Isn't this why they come with those plastic shims?

Generally to push the cleat further out a bit to get a good purchase on the pedals*.

*eggbeaters recommendation with their shim.