Hello Darius,
Those positive comments I posted are so well deserved.
Thanks for replying on what you used. I too now use APP for any large mosaics, and I agree with you that it's much better and easier to use. It was Manuel who persuaded me to try APP after pixinsight kept hanging without any notification being given. It is only by monitoring the RAM that you can actually confirm that it's a memory issue.
If anyone is attempting this with only 16gb and pixinsight hangs, try downsampling the panels. The great advantage of APP is that not only does it inform you of insufficient memory, but also suggests the amount of downsizing needed to complete, and then continues and finishes it. With 32gb of RAM pixinsight will probably be sufficient for anything other than really huge ones.
I'll butcher a post on the pixinsight forum with some relevant comments matching my own experience with pixinsight just hanging. Hopefully I'll be able to successfully share them here.
Cheers and CS,
Ray