With these things, there's a million and one ways you can get a desired result. You can use thinner sway bars, maybe thicker oil, maybe a combination of the two, etc. Here's a good read. It's X-ray's Buggy/Truggy setup book. It'll give you an overall idea of what effects what. It's specific to their cars, but the fundamentals are the same no matter what ride you have.
http://www.teamxray.com/teamxray/sho...p?file_id=4461
Not sure if it's same on a plane but dual-rate is related to EPAs. End point adjustment allows you set how far your servo travels left or right. There is EPA for each. Dual-rate is the same thing but it adjusts the EPA setting for both left and right at the same time. By turning down the dual-rate, you essentially makes the steering less sensitive because the wheels don't travel as far with the same amount of throw as they would if you cranked it all the way up.
Proper radio setup is often overlooked. You should set your EPAs up with the Dual -Rate set to it's maximum so that the wheels turn as far as mechanically possible. This way, when your D/R is at the max, you have maximum steering and vice-versa. Some people forget to max out the dual-rate before adjusting their EPAs and that sets your D/R outta whack.