I've been a member of the NWCR for about six years. There are so few of we maintainers around, and comparatively few studies of maintenance (as compared to weight loss) I'm happy to help out.
The Registry accepts non-US members, if anyone's wondering.
I find some of the questions hard to answer though. The questionnaire assumes that you eat a lot of processed/packaged food. For example, do you eat "regular" or low-fat salad dressing? We don't buy bottled salad dressing, so whether we eat regular or low-fat depends on the recipe we're using that night.
Then there's a question about whether you eat cold cereal. (Yes) Then later on, you're asked to fill in a box from a list - Special K, Kashi Light etc. I eat either home-made muesli (no added sugar) or home-made granola (no added sugar or fat) so I just leave that box blank, thus creating a discrepancy. Once, the Registry emailed me because I forgot to answer a question, but they never got back to me about the cereal issue.
Anyway, it's a worthwhile exercise.