"Your marketing effort should start BEFORE the product gets built" is in contrast to others' comments (like "use your spare time to build") but I think you may be right. There is certainly risk, and the likelihood that enough people will be interested (and have the time) is difficult to assess. That's exactly why I need to start discussing the idea with people who know better than I do. Marketing is a completely new challenge to me. I'll have to think about this further, but for now my primary concern is to finish the design documents, at which point I'll have something tangible to offer up for feedback. Thanks for keeping the mammoth task of marketing on my radar.