Time to lose 20 inches...
I made my cut lines on the inside of the roof because I was able to use one of the roof support members as a guide.
I wanted to make the cut as far forward as possible, but also wanted to keep it slightly back from the C-pillar to ease future bodywork/sanding. On the inside I noticed the factory 3-point seatbelt mounts and decided to make the forward cut just behind those. The rear is 20" behind that.
You can see here that I cut some wood scraps to use as a guide for the sharpie with the roof member as the fence:
After making the cuts from the inside I move to the outside and figured out where to cut based on the previous cuts:
...and there she goes:
That thing is heavier than you'd expect; 50-60lbs I think.
