@seppim I have no idea since I did not test loading it with memdisk. I did not look but I suspect the iso image may be larger than 2GB (thinking memdisk is a 32 bit application and not a 64 bit app. But this is only a guess). I know when I was testing the boot.wim file on the iso was 1.3GB in size.
I was able to get it to boot in uefi mode here: https://forums.fogproject.org/post/140212 but in bios mode it complains about needing bootmgr.exe in the iso image.