Sir, double fisting can only be done one in each hole, and YOU MAY END UP WITH A GIRL UNABLE TO CONTROL HER SPHINCTER. Unless you want to keep her in Depends, I do not suggest it. Besides, where's the fun in a good ass fuck if it's looser than her cunt? You really want to hear her reaction when you shove yourself balls deep in her ass. That gasp is precious, I assure you.
Thhere's a picture of my punishment pole and tool racks attached to my other post. The impact tools are arranged in order of striking power, left to right.