We have a portable roll around AC unit that we use at home. It works great and I never gave it a thought for the HI-LO. They do not take up much room and the vent hole is no more than a dryer vent.
My roof top works great but consider some advantages here by not having the extra wind drag and weight on the top, nor the potential for leaks.
I am about to start on a major rebuild due to water damage and this might just be something I will do too. We can use the same AC on the road, we sure don't run it at home when we are gone.
Thanks for a good suggestion.