If you are going to buy a servo reverser, I would suggest you look at the EDR-106 Servo Reverser.
This type of reverser is much better than the Futaba. There is no adjustment screw to mess with, because the circuitry stays stable at all temperatures.

Here is the web site.....they make some good stuff. You would want the Pro Servo Reverser Y for split elevators.

http://electrodynam.com/rc/EDR-106/106faq.shtml
http://electrodynam.com/rc/EDR-106/index.shtml

Greg