Can you also incorporate a limit, how many tiles shall be geoconverted at once?
The exact amount before geoconverter crashes seems to be depending from memory sise and tile size.
It's not totally straightforward, but I'm looking at something like that...
When the tile download and stitch is done I have the stitched images and coordinates for one (or more) level 9 AFS tiles.
The stitched image sizes don't match the AFS grid, they had to be just a sensible multiple of 512px.
I'm setting the coords of the level 9 square in the TMC and GeoConvert figures out how many tiles to make based on the specified levels (11 and 12 in your case).
To get GeoConvert to process less in one go, I'd need to generate several TMC files with the Level 9 grid coords subdivided.
Of course the extreme option is to run a new GeoConvert process for each tile.
If GeoConvert can always handle 16 tiles, that would look something like this:
Level 9 - 1 tile to process
Level 10 - 4 tiles to process
Level 11 - 16 tiles to process
Level 12 - 64 tiles to process (split into 4 GeoConvert runs)
Level 13 - 256 tiles to process (split into 16 GeoConvert runs)
Level 14 - 1024 tiles to process (split into 64 GeoConvert runs)
Level 15 - 4096 tiles to process (split into 256 GeoConvert runs)
It's a shame that their tool seems so flaky and this is necessary.
I'll do some testing this weekend.