After seeing the joist layout it occurred to me that my original light layout, with some of the lights in line with the centre of the room, would not work.
The red sections are steel, the yellow is the projection screen mounting area. The white lengths represent the wooden joists, and note that the short lengths on the right are not in line with the room.
Calculations told me I’d need about 5500 lumens, which actually equated to about 23 of the Philips hue bulbs I wanted, which is up from the original 11. This layout gives us 16, it doesn’t need to be a bright room and worst case scenario we add lamps. That’s what I’m telling myself to avoid stressing out over it.
Also pictured are the four ceiling speakers and their coverage in their position, which seems to be ok!