Other adapter plates use a profile that is acceptable with all deep Tuttle boxes including ones not made from composite.  A good fitting composite Tuttle box however needs to be slightly sanded to get a very tight fit into it's box.  So if you're using a competitor's adapter plate on your GoFoil it will be loose, especially if you have already slightly sanded your composite GoFoil Deep Tuttle to fit into a board-installed box.  Our adapter plate was designed with this in mind. It is a nice tight fit.  Complete with brass T nuts Stainless screws and alloy washers.