meant 531's...that is what i have..i am really considering going ahead and ordering 4 of the ds811 digitals...not too bad of a price for digital, considering the brand name ....i am going to stay with jr because i have already bought some aluminum arms for the jr spline gears...not sure why i said 537's .....i wish they would just quit changing the numbers so often....the main reason for considering the digitals is they would have the holding power near the center...or a very small amount of dead band around neutral.....with the control surfaces as large as they are on this plane...that could be an issue.....i did read a post from someone using standard 3003 servos on this plane...so apparently torque is not that big of an issue...