[18:30] So I was looking into seeing if I could obtain a valid simulation for the large 2160px displays. For 4:3 displays, I'd need 66mm of visible area.

On AliExpress, there seems to be quite a lot of options for achromatic lenses. It's kind of suspicious though because I'm not usually able to easily find so many diverse options using AliExpress search. Maybe they finally fixed / tweaked something in their systems? Well anyway there's a decent amount in the sub £10 range, but the focal distances are all quite large so it means will need to use multiple.

Well I was happily using 24 degree FoV in the simulator and I just realised that optics don't work with horizontal / vertical FoV's but the largest diagonal FoV. For the 2160px, this would be 30.5 degrees and for the 2560 this would be 36 degrees, so even if the 2560px was cheaper, I couldn't use it with a flat combiner. The quad 1440px = 2880px idea I had a few months back would've had no chance.

[19:15] A solution... fails, due to the proposed optical combiner.