Bad form replying to my own post, but a quick follow up.
I 3D printed a grid to space the LEDs away from glass/vellum. First prototype, and I’m blown away by the difference.
There’s a tiny little bit of bleed from one square to another (only really noticeable when one pixel is bright white, and the next one turned off, but for a first pass it looks great.
Need to work out how to take a decent video of it now, sometimes getting a flickery effect on camera which can’t be seen by eye.