[U-Boot] do i have any chance of booting a vxworks 5.5.2 image with u-boot?

i know u-boot has a "bootvx" command for booting vxworks images, but from what i read here:

http://stackoverflow.com/questions/24114948/vxworks-portingdm8168

it's only vxworks 7 that supports u-boot as its bootloader. i know precious little about vxworks, i was just handed a version 5.5.2 image and asked whether it was possible for u-boot to boot it.

do i have any chance whatsoever? any guidance would be useful.

rday