I suspect that you have a fairly big item to use that much memory with a moderate tolerance value. One thing to keep in mind is that the tolerance value is really more of an estimate of "Maximum Tolerance". Internally, Meshcam will use a much smaller tolerance value for all of the calculations. I suspect that 6LB foam can never hold anything close to a .025mm tolerance so you're safe to make it bigger and you'd probably never see a difference in the output.
Also, if you do parallel finishing only then Meshcam tends to use less memory because it can skip some big calculations used for the roughing, waterline, and pencil options.
I'm glad you like the multicore behavior. This was something I put a lot of effort into a few years ago and I never get tired of seeing all eight cores on my laptop pegged at 100%.
-Rob
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)