I'm stupid when it comes to certain software techy things - what are the assets that need to be provided?
I think a 16:9 8K (7680x4320) at 300ppi would get us about 29.3" diagonal, a 16:10 8K (7680x4800) would almost right on 30" (30.2) at 300ppi
I suppose you could do 325ppi and end up with a 27" and the 3X UI scaling would work just fine - 108ppi (standard 2560 screen); 217ppi (5120 retina screen), and 325ppi (8K retina screen), or you could have a larger screen (32") and relax the density to around 300ppi
We'll see 8K soon enough:
Dell's already selling an 8K 32" 16:9 for $4999