Several back pain sufferers over on the
www.bentrideronline.com site claim recumbentcy cleared theirs up. They say that a winter layoff causes their back pain to return in about six weeks. This has been my experience also. IMHO I advize to leave the crank forward models alone, you need a full backrest. Start with a used Sun EZ-1 or better yet, choose one of the 2010 Rans lineup, as just detailed on their site.