The hhkb looks like it has some sort of tube/socket situation, I’m not sure how to find magnets like that. Judging from this clip it looks pretty stable though.
I only found this clip so far about the dygma raise attachments, but they seem happy with the magnets. They look similar to the ones on the hhkb.
Stagger would probably keep it more stable, but I already have an “open sandwich” Levinson so I’ll give it a try on that one