I don't know how RTX works and what its vertical accuracy is as I use tower delivered RTK.  With RTK it would be possible but very difficult in my opinion.  You'll constantly be watching the elevation numbers and toggling your hydraulic remote to TRY to maintain a level grade.  If you have Field Level II unlocked it would be EASY.  Just use Point/Slope mode and set your slope to zero degrees slope.  For what it does the Field Level unlock and hardware is very affordable.