Tabs question and existing DCRs.

System

I am about to begin using tabs. I will be switching from iwov to xml as my dcr type in order to do this. Here are my questions.

If I add tabs and switch from iwov to xml in my templating.cfg will my users be able to edit existing dcrs that used the iwov style without tabs (testing so far tells me that it's not going to work)?

If the above is true, what can I do so that users can edit existing DCRs that were created prior to the tabs changes in my datacapture.cfg?