Since I was determined to use 1/2" material in the upper story of the silo, my final drywall bending challenge was the most difficult. To get the radius just right, and keep the sheet from breaking, I built a form out of leftover drywall and lumber scraps. Then I robbed the house of several bath towels and used them to saturate the drywall sheets with water. After sitting for an hour or so, they easily sank into the shape of the form.
Next, I screwed some crossmembers into the form to hold the drywall in place while it dried.
A perfect fit...now that I've become an expert at this, I should never need to do it again.