Yesterday I posted a design for a simple solid-state
flap motor controller. I didn't know it at the time,
but there are many motor controllers available in an
integrated form. This general type of reversible
motor circuit is called an "H-bridge". Which just
goes to show that it is easier to find stuff on the Internet
if you know what it is called.

A better explanation is here:
http://www.ikalogic.com/H_bridge_1.php

And circuits designed to do exactly this job are here:
http://www.national.com/pf/LM/LMD18200.html
http://www.national.com/an/AN/AN-694.pdf
http://www.cadvision.com/blanchas/hexfet/np-s.htm

And this does much more than we need, but could be controlled
by your flight computer or autopilot or whatever....
http://www.robotshop.ca/home/suppliers/dimension-engineering-en/dimension-engineering-syren-10.html
http://www.robotshop.ca/PDF/SyRen10-20.pdf

With any of those, the switch wiring is extremely simple.
An SPDT is connected with center pole to fused +12V.
The other two leads are connected via the limit switches to the P1 and P2
(ikalogic) or A and B (Cadvision) pins. With the National chip,
the wiring would be slightly different. I'll leave the details to
someone who really wants to build it into the airframe.