I have been following the development of the Owl filter adapter for some time.
I have refrained from ordering one pending some independent reviews so I am eager to hear how it performs!
The problem is to have 52mm filters with low frame height, the only downside it has (so far). If it is really light tight, I have to test (and I do have some doubts, as many normal adapters, even the most expensive ones, do leak...). Unfortunately not that much time currently availbale for such.
Step adapters cannot be mounted, it has to be a low height 52mm filter frame! (So a Baader-U filter for instance needs to be remounted)