Seeking ideas for attaching hangboard to the AmazonBasics pull up bar

Hey guys, I've got an AmazonBasics pull up bar, and I'm trying to figure out how to attach a hangboard to it. Two caveats:

1. It can't be hanging from cordage/webbing--that's the easiest solution, but I've used that a few times, and I find it makes things more inconsistent because it's impossible not to have some swaying while you're hanging.
2. Preferably it would be easy to attach/detach because I still plan to use the pull up bar as a pull up bar. But the pull up bars are cheap so if I can't do that it's not the end of the world, I'd just get a second one.

I've looked at the Blank Slate training boards, but they're too wide for my door. My door is 24 inches wide with 2 inches on the right side before a corner.

My current idea is to drill two holes in a plywood board at the locations of the bars that stick toward you on the pull up bar, and attach the hangboard to the plywood board. But I'm worried that will sway the same way that cordage/webbing setups do.

I followed this: https://betterclimberproject.wordpress.com/2013/02/13/diy-doorway-hangboard/

and it worked well.  Also check some creative ideas on this thread: https://www.mountainproject.com/forum/topic/112506185/mount-hangboard-on-doorway-pull-up-bar