Obviously, I don't have a Hopper 3 yet, but I did some testing with my sling Hopper. I've been using the m2ts format for Blu-Rays.
I decided to try for a mkv. I use DVDFab 9. Using the Blu-Ray of Avengers Age of Ultron I did a MKV passthrough. It made the file in just under an hour and the file size was 29Gb.
I use TVersity for my DLNA server. I started watching the movie on the hopper and it played fine for a while. It started to stutter but I think it may be because my computer is old and couldn't keep up with such a large file. To give you an idea of how old it is. The manual for the motherboard is copyright 2007 and the computer only has 2Gb of memory.
I know. I really need to upgrade. It's on the list but never seems to come to the top.