Hello again! I have spent some time diving deep into your parameters and some of my own with UF6 and it's been fun. But on two of the final renders of my own there are some artifacts and I don't really understand why they're there - not sure what went wrong. Would you be willing to take a look if I send them to you? I'd also send the two I did of your parameters so you can see the results of the colouring algorithm I mentioned. (And even with UF6 two of the renders took over 24 hours!)
I love these zooms, especially the ones like this one that show really beautiful and somewhat unusual shapes. I have previously used Pauldelbrot's (from Fractal Forums) colouring algorithms for UF zooms and have been thrilled with the smooth, silky results - have you tried?