Just to put a spin on things, what if James didn't have a middle name? Since we've never seen a canon middle name, it wouldn't be defying canon to not give him one.
Dark_Lady_Z brought up how there was nothing on his gravestone. Usually people's whole name are printed on their gravestone. So if it's really stressing you out, don't give hime one! Or you could give him just a letter. Like me. My middle name is just one letter (an initial).
Hope this helps!
~Morgan
