It seems as though materials saved as Mxed V3 are not backwards compatible and won't open in Mxed V2. I am currently using both FZ6 and FZ8 with their respective plugins for maxwell. Because materials edited and saved with Mxed 3 (from the plugin for 8) are no longer able to be edited by FZ6 using Mxed 2, I don't want materials accidentally saved as Mxed 3.
To alleviate this situation, I've compressed Mxed 3 to force the plugin to use Mxed 2. It's an odd solution but it seem to be working fine so far. The plus side is that none of the materials become corrupted and unable to be edited when using them with FZ6.
I could go the opposite way and have the plugin from FZ6 use Mxed 3 materials but when it does, the material preview for maxwell does not show in the Surface Style Parameters Dialog. Maybe an update of Maxwell Z for FZ6 would fix this.
Another BIG reason to continue using Mxed 2 is that it allows you to keep the texture (and color picker) window open and switch from texture to texture in the editor. In Mxed 3, I have to close the texture and color picker dialogs each time I switch to a different texture or color. Is this true for everyone or just on my system? If it is a "new feature", it's a poorly thought out, inefficient, annoying time killer.
Do you see any reason that mixing FZ8 with Mxed 2 and Maxwell 3 might cause problems?