Not sure if it's worth adding to the documentation but I found I had to add the following to the end of the fstab command otherwise the system would not boot cleanly.

,x-systemd.mount-timeout=30,_netdev

The line in fstab now looks like

mfsmount /mnt/mymnt fuse mfssubfolder=mydir,allow_other,x-systemd.mount-timeout=30,_netdev

I think it was trying to mount mooseFS before it had fini

Description of the format: http://archive.dimacs.rutgers.edu/Challenges/