He said he had 3 brass shims originally, and since the aluminum shim he bought was as thick as two brass shims, he used it and one brass shim to get back to the original height, therefore providing he's got his facts straight, he's not changing his compression.

Brass Shim
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Aluminum Shim
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3 Brass Shims
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1 Brass Shim + 1 Aluminum Shim
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