Ok, been slacking a bit so time to get back at it. Now that I have high speed I can post a few more pics.
So, where did I start. The basement was a bit of a mess. I put the framing of the riser together and there it sat for a few weeks.
And this is how I cheated by getting two of my chairs out and hooking up the projector. Wasn't even in the theater rather just on the game room wall.
Just on the gray game room wall.
Now all the of the chairs are back in their boxes as is the projector.
Now did a bit of cleaning
And started with the framed riser. Note, used 2x12 ripped down to 9 &7/8" for outside edges and used 2x10's ripped down to 8 &1/4 with joist hangers for the inner joists. This would allow me to put 1/2 OSB on the bottom of the inner joists to create a cavity to fill with insulation while keeping the insulation (and the OSB) off the concrete.
I then went around and used the rubber uboats to level. The gets the wood off the concrete so I don't need to use treated and gets rid of any wabbles due to the uneven floor.
In cases where I didn't want the u-boat sticking out, I cut off one side. In two instances where the floor was slightly uneven, I actually cut off one side and put the remaining side under the joist rather than the base as it was thiner in certain areas. Note in the picture below of the intact u-boat that one side is slightly thicker than the other (left side slightly thicker). I slid them down the joist until they were snug.
Because I then wanted to flip the riser to attach the 1/2" OSB to the bottom, I predrilled the rubber then screwed them to the riser so they would not come off or shift. Everything was level with no tipping when you walked acrossed it and I wanted it to be that way when I put the riser back.
I then flipped the riser over (note, still in two pieces) and glued and screwed the OSB to the riser.
One down, one to go.
And second part done.
Then flipped back over and put into place. Getting very heavy...
Now I have a nice OSB bottom that is not touching the floor.