Merry Christmas.
I have had a MyClip ipad strap mount for some years. It has been very good. Holds iPad securely and adjustable for various size iPad types.
Not inexpensive, but works well.
Video below is for aerobatics, but it is the first video I could find.
Search for myclipforipad
https://youtu.be/mB_w90G3SYM
I agree, myclip is perfect for this. I used it for years. Until I didnt want to accept the headaches anymore caused by the constant neck down / neck up movements. (Then I mounted the iPad higher, just high enough to be able to see by moving my eyeballs down, but without neck movement. However, the OP explicitly said that he didn’t want to hear reasons why kneeboarding is not the right approach in the first place…)
Myclip doesn’t allow to hold or charge the Apple Pencil. I do not recommend to use the Apple Pencil in flight anyway: it is too finicky and the batteries in the pencil tend to be flat when you need the pen most. Be this as it may, almost no cradle is able to securely hold *and* charge the pen.
You can always write down your clearances with your finger in fore flight and all other nav apps.
Also, obviously, in flight (unless you using autopilot) you operate the nav apps on the iPad comfortably with your left hand, while most people can only handwrite with their right hand.