This is already much better. Thank you.

I took it upon myself to try adjusting the rendering levels. I appear to get improved performance by setting int level = 2, minfov = 60, minfov /= 3. That seems to work well with only level 3 and 5 available and doesn't try to load too much level 3 detail at once. But that should probably only be changed when offline cache is used. So that might be worth considering. It might also be a worthwhile to have Level 2 images in the cache as well.
I should also mention I'm testing this on a Pi4 8gb with a USB3 SSD system drive, so the read speed are about as good as it can be on a Pi4 B+.
Thanks again.

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