I was working with 3 teams which had mid-week start/andend of the sprint. They were starting on Wednesday afternoon (17:00) with planning and finishing sprint an hour before (16:00).
Comparing to monday-friday the advantage of mid-week cycle is that there is a weekend in the middle of the sprint, when already some issues should have been discovered.
I'm far from advocating working on weekends, but as software development is mostly thinking I have experienced that some developers just thought over some issues during the weekend.