WHY NOT CUT A PIECE OF PLEXIGLASS TO WIDTH AND LENGTH YOU WANT GLASS TO BE IN CAR MEASURE CUT ROOF. THEN MEASURE DEPTH OF GLASS (HOW FAR THE GLASS HAS TO SIT IN CAR TO BE EVEN WITH TOP OF ROOF) MAKE A FRAME TO THE WIDTH, DEPTH AND LENGTH YOU NEED AND HAVE A LIP COMING OFF IT TO SIT GLASS ON. PLEXIGLASS WILL FLEX SOME SO IT SHOULD SIT OKA EVEN WITH A LITTLE CURVE OR WHAT NOT. THEN TINT THE GLASS SPRAY THE NEWLY ADD METAL TO MATCH CAR GET SOME WINDOW SEALANT LIKE THEY USE FOR WINDSHIELDS PUT IN LIP PLACE GLASS ON TOP LET IT SIT FOR AS LONG AS NEEDED. THEN FOR THE LITTLE CRACK LEFT BETWEEN GLASS AND ROOF MEDAL BUY SOME WINDOW TRIM AND GLUE IT IN PLACE.
THEN YOU ARE DONE

NOW I HAVEN'T DONE THIS JUST THOUGHT IT UP FOR MY HATCH A WHILE AGO SO I DON'T KNOW HOW STRUCTURALLY SOUND THIS WILL BE FOR YOU HATCH YOU MIGHT HAVE TO AD SOME SUPPORTS BUT IT GETS WHAT YOU WANT DONE AND PRETTY SIMPLE FOR THE MOST PART.IT MIGHT EVEN BE A BETTER WAY TO DO IT THIS IS JUST WHAT THOUGHT UP
LET ME KNOW IF YOU ARE GOING TO ATTEMPT IT I WOULD LIKE TO SEE IT FINISHED

O AND SORRY ABOUT CAPS TO LAZY TO RETYPE