Those plates aren`t particular to that model
As FN pointed out - they`re commonly used with plastic toeclips and that model is plastic. The idea is to distribute stress as evenly as possible over the front of the plastic .
Suggest you skip the idea of using the washers instead. You should be using those on the backside under the nuts. Yeah, I know - you didn`t mention nuts. They`ll be part of the package and without them I have no idea how you planned on attaching these.