Thanks again Norma for bringing this flour to my attention and leading to me putting a sample bag through the wringer. After reading the beginnings of this post I promptly got a bag. I proceeded to do a side by side test including baking in a Ferrara. The GM seems indistinguishable from Caputo. During dough making, balling, stretching and baking, I and the pizza eaters around me couldn't distinguish between the two doughs. It may have been my imagination, but I thought the GM smelled better when cracking open the cornice.
I posted some poor quality pics for those that might be interested in the flours next to each other, balled dough and cooked pies (just the GM).