From Will -
"When I’m using a Gri Gri so it won’t matter if the belayer get slammed into a wall feature or whatever, the rope still stop even if the belayer is maimed. Maybe., and Petzl does say this is OK. But one of the best ways to make a Gri-Gri feed is to block the lever down, which is what will happen if the fall pulls the Gri Gri hard into the first piece as will will likely happen with a high-load fall. No, definitely don’t clip the (anchor as the) first piece if you’re using a Gri Gri! Unless you’re tied down.."
Interesting. I recently witnessed a light woman catch her much heavier partner falling off a very steep climb (very little friction). She was not tied down (this is the gym after all). She was belaying with a Gri-Gri. She got pulled all the way up to the 1st draw. Then, her abdomen, harness, Gri-Gri, the whole nine yards got jammed into the rope biner of the draw resulting in the Gri Gri's cam having no room to pivot up to lock the rope. She eventually put on the death grip with her brake hand and prevented her partner from decking out. But it did take her half (?) a second to figure out what was happening. And when both of them stopped moving, she was hgher off the floor than her partner (he had fallen past her in other words).
She was quite shaken up mentally by the whole affair. I had my eyes opened by the incident. So, yes, there is good reason for Will to write the above!