Matey, go with what you think is best. If you take it to -12db RMS, it does get louder than the mix, but, i leave that to you too. Personally, even matched volumes is OK, really! As long as something more was rescued or gained out of the mix overall, even that would suffice. MY approach was to work with the same or slightly lowered gain structure. And moved into areas of lo/mid/hi bands blends and seeking perhaps better articulation and more clarity, if I could.
This is more or less like your typical client. Coming back from an adventure of recording and mixing, most times in a tunnel effect... At times they get it just right, and then there are times when you feel like a butcher in an abattoir, moving carcasses around.
Hopefully, this ain't the latter.