Be careful of your throw distance with this projector/lens setup. Almost tripped me up. The 50EX has a puny zoom ratio (1.6x), which means your projector placement may have to be closer to the screen then you'd like (only 15' throw on a 110" wide x 47" tall 'scope screen for me), and a manual zoom that's going to cause you to have to get up and physically putz with the projector lens every time you change the aspect ratio. Or, you could leave it in place as it's designed to be and suffer the slight distortion & loss of resolution in 16:9 mode.
That's a compromise I wasn't willing to make, so the lens needs to be moved out of the way when you go back to 16:9 content. And it's not made to be used with a sled or other hinging device; you'd have to rig one up or literally remove the lens when you go back to 16:9.
Bottom line, I crossed off this projector/lens combination. If I had a longer throw or a bigger screen, it might have been a different story. Still no electronic zoom, though, and that's a bummer.