As I recall, my Achilles had 3 plastic plates: 2 under the 2nd deck section, and one above, attached with about an inch to an inch and a half of extension. They were, at a guess, about 6" wide, and 3 or 4 inches deep. A couple of aluminum plates would do the trick; probably 1/8" or 3/16" thick. Round off the upper edges, and you're good to go.
jky
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