That was the reason, to create this plugin. I should allow users to enable server-side compression and be able to use the WebDav saver. ...
BUT as you can see on some responses to the thread here, there are also problems with if-modified ....
The whole process seems to be very brittle, if server and client settings aren't matched. It's really hard, to replicate server configuration problems, because you have to rebuild a user setup and hope, that it will create the same problems. ...
It seems he found a solution for an Apache setup with WebDav + compression enabled, which uses the TW default PUT saver.
So the plugin described here, may be usable for other configurations.
have fun!
mario