From my experience with biplanes, I always started with 0. I had a 1/3 christian eagle that worked best with 1 degree neg. It penetrated the air better in landings. I,m building DP's ultimate now, its wings are 0, but the tail has 1.5 (not sure which way, book is in the garage). I know someone to call, If I find anything out I'll post it. Sorry I couldn't do more.