I tested the latest "WIP" for the next release, and I think I've got the problem resolved, but I need testing, people!! Any "WIP" testers using large F:, please check the latest one out.
(Of course, use X-Selector or run as an app, to avoid headaches)
On my 30GB drive, the LBA48/Big F patched 4977 BIOS boots - but when I use MXM_Patcher on the executable, it hangs as previously described.
So the problem is when MXM tries to initialize G: on startup.
I have one more check to do - eliminating G: init when F: is not present. These options only apply when MXM intializes.