I have the keyboard in the picture (the Freestyle) but I do not have the "tenting" accessory that is holding the keyboard in a vertical position. He was suggesting I get/build that.

I have the VIP accessory which lifts each half 15 degrees, but that's still pretty far from 90.

When you make a 90 degree angle with your elbows, it is natural for your palms to face each other. When you point your palms down for long periods, it causes torsion in your forearms which can cause pain.

I've reduced that pain by using a vertical layout keyboard.