Custom inspector for fixed-size array in object in large inheritance tree?

Hello. I have an object that is fairly high-up in an inheritance tree that contains a fixed-size array. I am wondering how to implement this such that Unity shows the values in the inspector for the object (and any objects that inherit from it) without making the array resizable. I've tried putting the array in a subclass and writing a custom editor for that subclass, but Unity doesn't seem to be willing to use a custom editor for a single member of a object (unless I'm doing something wrong).