Made a serendipitous discovery. My 12F 16:9 format (with the centre being 5 inches above the bottom pegs) fits horizontally inside my 16F 2.39:1 format, just by adding 2" each side. That should hopefully mean wherever I position the top and bottom pegs should be compatible with either set up. 16F is huge, by the way, so I wouldn't use it often except for detailed 'scope shots.
The pages are 25cm tall ('cause that's the newspaper print roll sliced in half). "Official" animation paper is way too tall for most modern use since rarely does anyone animate in 4:3 nowadays, so I don't see the point in going with the standard. Also pre-punched papers a rip-off.