| Pizza Lord |
No. That makes no sense. That's a fantastic, unscientific, impossible scenario. What kind of game are you playing?
On the other hand, yes.
You just need a reason to make it reasonable. Something along the lines of "This plane's gravity field is 10 feet above the surface and lessens considerably above." That should be sufficient. If you're asking if you can, as a player, create such a plane; that depends on the power you're using and whether the GM thinks it's either permissible or cool enough to do it anyway.
If you want to discuss the ramifications or what kind of craziness it might cause or shenanigans, then you'd need more details of how much less gravity is (moon-like) and how high the demiplane's 'ceiling' is, stuff like that.