I am sorry Marty, I should have read this more carefully:
Even though your 2x4's were really 2x4 You may have to "sister" those roof rafters because now the snow won't immediately melt.Can be heavy snow loads on the roof,2x4 construction.
You probably thought that so you mentioned it. Check your local code for snow load and pick the right rafter.
PS Your North Latitude and those 3 ft overhangs really cut your cooling load from what you report.