Mk007 Hey MK. I am slowly figuring my particular issue out, but I wonder if I might be able to help you.
I have setup many regular static "always-on" conference bridges with Elastix and my guess is you aren't trying to do exactly the same thing as me right now, but I may be wrong. My biggest one can handle 20 participants but I expect it could scale much higher. My newest implementation is virtualized in a data center and I connect directly to an SBC on the same subnet so I could probably handle 100 participants or more.
What is your goal and objective?
Thanks,
Michael