OK, I really am a doofus. The problem: I own a TON of .dae files I purchased in SL, and a whole bunch of them have permissions to share them on other grids, as well. So, I've been trying to upload them to Opensim. In Firestorm, I go to "build", then "upload", then "mesh model" and I select the file from mij harddisk. "Open", set LOD to "low" and pick "calculate weights and fees". There is... a really long time that goes by, like 15 minutes or half an hour even. And then, a popup: "(item name) failed to upload: missing physics_convex block". What am I doing wrong?