Set the final output size in pixels FIRST (or earlier in the steps), and set a default mosaic piece size (changeable) that makes sense for that final image size.

I just created a pretty unusable mosaic, which took a half hour. The program "worked" and did what it does correctly, but this final image is useless, because I wasn't sure what to set. The mosaic pieces are too small the way I set it this first time. I'll have to experiment probably 5 more times to get close to what I want. Mosaic pictures like this have some default ranges to make a pleasing image and the program should default to those. I don't know what those default ranges are right now. You're the experts.

And the final image size should be exactly settable. If I want a final 8x10 at 300dpi or ppi then that makes the final image output 2400x3000 or greater but with one side being exactly 2400 or 3000 which I can crop to proportion later. The program could also add cropping as a final step, but that is beyond what I expect. Or the program could crop to proportion as an early step on the original base image then process the final mosaic exactly the size I want in the first place--this is probably the best way to go.

It's always something!

The program as it is does work as described, and thanks for that.

Here's the steps the way I want:

0) Load/index the pics to be used in the mosaic (doesn't have to be done every time)
1) Load base image
2) Crop the base image to proportion (4x6, 4x5/8x10, 5x5, 5x7, 8 1/2x11, or other enterable in pixels
3) Set dpi or ppi size (except if final output was entered in pixels)
4) Default number of mosaic pieces for the output size wanted (changeable)
5) Process
6) Preview and save.