I'd stay with the longer dimension - 41" if I were you. From my experience the longer number works out better. I like to use the Chuck Cunningham standards, then add a small amount of length forward the step. Chuck says use 53% in front of the step, I like to use 55% and work from no less than the 80% number - which for you would be 41.6". This is just what has worked out for me best. The little extra in front is just a little extra measure of insurance against nose overs.