I did the same thing as ADDUpstate for the side panels. Just lined it up with the "goal post" uprights.
As for the friction thing, there are a couple of ways that it could be done...
1) Build the upright posts, line up the bottom, tap the top into place from BEHIND THE FUTURE WALL TOWARDS THE VIEWING AREA. Any damage to the ceiling will be behind the uprights. This was metioned somewhere in this thread, but could easily be missed.
2) Build the uprights, line up the top, and tap the bottoms into place. If this is on an unfinished floor or stage, then no damage. If built right, it will hammer in place and still be snug enough to screw into the floor and ceiling.
3) Carpet your room first, then when you put the uprights in, you have a little cushion (literally and figuratively) to get the uprights in place. This is what I did. We tried to make the room so that it could be used as something else later on if/when we ever sell the house, so I carpeted the whole floor, and then put the seating riser in place and had that carpetted separately. I didn't build a stage, although I have thought about a small faux stage, but honestly I like the look now. If I didn't have a false wall, I would want a stage for sure. With the false wall, I like the solid, clean, one surface plane wall. Anyway, this worked great. I actually lined up the bottom, had someone else push down on the post (into the carpet/pad) as I lined up the top. Then I made my minor adjustments, screwed in the top, and secured the bottom. Worked like a charm and I didn't scratch the (painted) ceiling.