Installing hatch glass- not working

[fusion]

Is the hatch glass much harder to install than the windshield?  I am finishing up a 1976 280z build and am installing the glass.  I have brand new gaskets from vintage rubber.  The front windshield was a bit off a pain but got it on the first try.  

The hatch glass is seeming much more difficult.  The hatch is off the car and I thought it would be easier to install off the car rather than on the car.  I am using the same rope method.  With the front windshield, I was able to slide the glass/gasket into the lower pinch weld and then use the rope to pull the gasket around the pinch weld and use hand pressure to walk it around the sides.

With the hatch glass, I can't get it started on any sides of the pinch weld.  The top and bottom are especially not very close.  I really don't have a good game plan.   I did have someone helping me.   We gave up after about an hour and no real progress.  When we got one side sort of close, the other side would be going the wrong direction.  I am using 3/16" (4.8mm) rope.

I have seen a couple videos online and they basically just set the glass/gasket into the opening, flip the hatch over and start pulling the rope.  Looks super easy.  Not sure why it's so hard for me.  The glass did come out of this hatch, so I know it was in there before.

The new gasket is very robust and I'm sure making it more difficult, but I believe vintage rubber is generally regarded as a quality manufacturer.  The hatch is awkward to handle and manipulate which isn't helping either.  

Any advice is welcome. 

 

Thanks