As promised, pics of the grind transfer adapter are attached.

Thank you so much for the info, Tamas. This is really helpful!

I now have a much better understanding of how this works in the portapresso system.

It also seems like there is no way to grind directly into a standard 58 mm portafilter basket.

That's ok - I still want to get a Rosco mini. I'd better reach out to Ross. I wonder how long it would take to get one!

Very excited