I've tried every possible combination of grub menu commands:
menuentry "GhostBSD Loader" {       insmod part_gpt
        insmod chain
        set root='(hd3,gpt1)'
        chainloader /EFI/ghostbsd/BOOTX64-GHOSTBSD.EFI
That is the one everyone list when trying to dual boot with ubuntu.
It doesn't work. Grub output is:
error: image has invalid negative size
Tried other menu commands as I stated. Will not boot.
ghostbsd will boot using it own boot manager, but cannot get it to dusl-boot.

Has anyone dual booted ubuntu and ghostbsd?

This link shows same error I got: