tim if I understand you correctly, you only have the portion of the cage behind the drivers seat, no forward legs or A pillar hoop right.
If that is the case I did something years ago on an old jeep that you might be able to try. I used a piece of schedule 40 pvc pipe and notched a saddle in to the back end of the pipe to fit against the hoop behind my head and the front end notched to fit the contour of the windshield frame. I also heated and bent it up slightly about 8" or so from the back end to push up on the bikini top for more headroom, plus it looked a little more like a roll bar part that way than a piece of plastic pipe. I painted it black, wedged it in there and tightened the bikini top which pinched it in there tight. It never moved, and was plenty of support for the windshield.
this is the only picture I could really come up with, And I have no idea why it flips it upside down. I know the jeep was right side up when I took the picture.