What transmitter are you using? With Futaba you soften by using - expo, on a JR you use + expo to soften response.



Some transmitters actually have a display that shows the exponential curves, what you want is for the curve around neutral to look about the same on low and high rate, but on high rate as you increase towards full deflection the curve will get really steep as the control surfaces moves more to get to full deflection.
I would start with about -30 expo on the ailerons and elevator and -50 on the rudder for high rates.
Expo 101- What you are wanting is for the low rate and high rate to feel the same around center. That way when you flip from low rate to high rate you dont get too jerky.
I would be careful about *****g out the rate on the elevator too, I suggested about 16 degrees as a starting point for high rates. you can adjust it from there. If you maxed out the throw you could be up over 22 degrees and that isnt going to be fun for flying (yet)

If you have a good eye you can reasonably estimate it by finding 45 degrees and then eyeballing it from there. I would say be conservative as too much elevator can get you into a lot of trouble. Just guessing for an LT 40, I would say that you dont want the trailing edge of the elevator to deflect any more than about 1/2" up and down on high rates.

Like I said you need to be REALLY careful with high rates. The plane is going to be extremely sensitive and you have to get to low rates to take off and land. Take off and get up high, once you are at a safe altitude flip to one high rate at a time and fly around to get the feel for it. Especially elevator and aileron. The Rudder should not be that big of a deal.

If you sealed the hinge lines, you may try flying it on low rates first. Sealig the surfaces can make a plane a lot more responsive, that may be enough for you.[8D]