Well, now that Internet Tethering works again on non-carrier iPhones (i.e., those that are unlocked and not in use on an iPhone-carrier network) I've finally been able to upgrade while still keeping tethering working. This has required an update of my Vodafone carrier bundle, so that is now available on-line in the same spot as before (here). I refer you to my earlier post, Updated Vodafone NL Carrier settings, for instructions on how to install it.
Happy tethering!