Alright, here we go...
1. The Mits is a solid projector, but it has a fair bit of lens offset which means that you really must be putting it into a room with 8' ceilings and having it flush against the ceiling with the screen in, about, the middle of your wall.
2. 106" screen size is fine for this projector.
3. 106" may NOT be appropriate for your room and your setup. Typically, I find, people run a bit small when selecting a screen because they don't know that they should go a bit bigger. To determind your screen WIDTH - take your primary seating distance, and multiply it by .66 (two thirds). That should be the WIDTH of your screen.
4. I know nothing about dragonfly screens, but if there aren't reviews, and a fair bit of talk about them, I would be very wary of spending money on them. Carada is phenomenal for the cash.