Yes, the MPK for 42,99 € is 28cm x 28cm (like the original), i'm not realy sure about the roof thickness, because there is no specifikation in the text (but i think it would fit).
I had great respect for the enlargement of the cut to 40cm x 40cm but with the help of this website it was really easy... in
this article
i describe the installation of my Mini Heki Plus. You can also download it, in the PDF there will be more pictures at the end (but sorry, it is written in german).
Yes, i'm happy with my choise for that model, because it has clear glas (for watching the sky by night
), it has a blackout blind and you can open it more wide than the others!