I'm sure that you will be told by someone that you shouldn't but why not give it a try and tell us how it goes? I'd avoid doing it in rough terrain as there must be a bit more strain on the hinges compared to when it is latched. I also expect that it may close under air pressure at higher speeds. It will not be good for your fuel economy but it's a free world (well not really) so give it a whirl!

 

I doubt that the hinges are strong enough to tolerate driving with the hatch open. You'll find out soon enough.