I'm also using this PGYTECH holder for my 11" ipad pro. The description says it will not fit the 11" ipad, but it fits with mine and I even have the cover with the apple pencil. However, it just barely fits. I really like how this balances the weight of the ipad over the controller.
Mine might be even simpler... I used Velcro on the back of the iPad and side of the holder/antennae. Has worked fine through 6 flights so far!! I do have a 3D printed holder on the way too.