Thank you for your prompt respond. That's 28% which is almost close to 30% of MAC. BFoote is correct for specifying 30% on this category. Even if speedracerntrixie didn't mention anything about his expertise it proves that you can trust this guy with regards to this aircraft. With no doubt, this aircraft can land on negative stability. The manufacturer is quite conservative for specifying the safe CG location. This is how I wonder that speedracerntrixie is landing this aircraft w/o elevator. On overall, it's you who feel the differences who made a correct decision for deriving solution.