Au contraire, if an X is irrational and uncooperative, it is all the more reason to keep things strictly business. Certainly, it is worth trying to reach an agreement through Ls rather than through the courts when X has indicated she'd like to do so. Avoiding unnecessary battles of will and offering constructive, unemotional responses cannot hurt anything. But it might be even more useful to communicate about custody arrangements through the Ls in such a case. So, "XW, I too would like to come to an agreement amicably. Thanks for your thoughts. I'll speak with my L and we will send you a reply responsive to your thoughts soon." Then, let the L's talk.