Fine Home Building Magazine had a recent issue about 2 or 3 months ago that dedicated a very good article on Basement Refinishing. I did read it and it did, specifically, talk about building the soffets. I tried to use their 'Search' feature to find the issue but it may not be 'listed' yet. When I looked under Basements, I found EVERYTHING but 'Finishing A Basement'. So, you may have to e-mail them directly. They offer some alternatives too if they're 'doable' in your basement.