one caveat:
just came across this, as I was reviewing older posts looking for code…
In your case, having 13000 pixels in each map/PB might be too much… but the goal is the same number of pixels, I think, so the CPUs are working with about the same amount of data each render cycle… so 13000/4 is roughly ~3000+ pixels, but do try to at least keep equal amounts on each PB…
You’re going to have to play with timing to get it to work right. Again, non-trivial # of pixels, so the syncing of multiple PBs on that scale will take some work/experiments. Keep us in the loop.