I've been making mods as zip files for a while now, and I seem to recall there was some requirement that the mods be packaged as a zip. But recently I noticed that I get almost half the file size if I switch to 7Z format. And, now that I look for some sign of "why am I using .zip?" I can't find it.
I'd love to save everyone (well, 70-odd people plus spacedock) some bandwidth by switching to 7z, but I'm a bit hesitant due to half remembering some reason not to use it. And not knowing how CKAN deals with it. If CKAN can't unpack 7z, then it's out as far as I'm concerned.