While I like to keep all that through the Ls for the most part, I also see the value of being able to work some details out on our own if possible.
My GF and her ex-H did do some side negotiations, but over e-mail with the mediator and/or Ls CC'd. A $500/hr attorney may charge 5-min to read a couple e-mails ($42) or 15-min to skim a whole thread ($125). If you must discuss offline to reduce costs, can you still use e-mail to slow down the negotiation process, reducing emotionality, and allowing both sides time to weigh options and reflect on what's important?