New Layout with sub on rear riser?

I've been playing around in sketchup and have been toying with adding a second row. The room is 17' deep and 20' wide with 7'1" finished ceiling using clips and DD with GG. I have a low support beam that is only 6'3" finished height that runs behind the main seating as shown. The projector would need to be mounted behind the beam and low. Since it's low I don't want people hitting it so I thought about putting my sub (SVS PB12 plus2) under it on top of the riser. I don't have room behind the screen wall so it would need to be in one of the front corners if not.

The extra six seats are nice but may cause more problems than they are worth with low head room. I would modify the riser so you don't step up until you are already on the other side of the beam.

I plan on 7.1 with 6" corner bass traps and 2" panels around the room that will be backlit with rope lights.

Any thoughts?

I've gone round and round on this one. The beam is 13' from the screen. If I box it in I would only have 6'3" ceiling height under beams on both sides of the room meaning you would have to duck everytime you walked around your chair. Matching the soffit on the other side would only give me about 9' of clear space between the beams.

What you can't see is a stacked duct run behind the screen. The ducts take up the top 30" of the wall then I have an opening for the LCR. Think of it as a 10' wide by 5' tall fireplace that is 18" deep behind the screen.

The wide layout is not typical but gives me 6 seats across and a 120" wide 2.40:1 screen.

I have not started the theater but there is no possible way to raise the beam into the joist space. The joists are sitting perpendicular on the beam which is the reason for the beam. Am I missing something?

Also the height above the chairs will be 6'1" with a 12" riser. A 10" riser would give me 6'3" so it wouldn't be too bad in terms of walking to your chair. It would be used mostly for children since it's just overflow. I looked at bar seating and it's still an option. I think any seats in front of the recliners would block the picture from the projector.

The finished height under the beam is actually 6'3". I made a typo above and I'll edit the post. The ceiling steps back up to 7'1" on both sides of the beam.

I was thinking mini riser with limited room in front of the seats. I'll have about 42" for the width of the riser

Cutting the joist and hanging them off the beam is interesting. Did you have an I beam? What did you use to hange the joists from the beam? Any pictures? I think it's more than I want to get into but I'm curious.