When we installed the underlayment on the steep roof section at the opposite side, Dski and I did it with 2 ladders, leap-frogging each other every 6 feet or so, over the 52' roof length. It was awkward, cumbersome, and tiring. Moreover, I want to try and keep Dski off the ladders as much as I can; just cuz.
I got's me a 10 ft length of 2" PVC pipe, a 10 ft length of slotted angle iron, a 4 ft piece of 3/4" PVC pipe + 2"-to-3/4" bushing, and cut a 10" dia wooden wheel.
The slotted angle iron slips up inside the 2" PVC pipe, so it is "adjustable in height". We slip a 1/4" x 4" bolt thru the holes at the correct height to keep the PVC pipe supported. The 3/4" x 48" PVC mast is inside the roll of the underlayment. The 10" wooden wheel at the bottom of the underlayment roll is self-explanatory. Donna-ski was in charge of "unrolling".
So, we are down to one big ol' sunroof