The travel is only 2 3/4" and is a screw type. The thing I like about those actuators is that when they reach the end of the travel and find some resistance they stop.
Others you need a sequenser to do that.
My all means feel free to post here if there's a way to share tips, tricks and how too's it will be great.
Like I said before the 51 is on ice right now as I am working on multirotor systems. see here: http://www.wimac.ca/forum/showthread.php?t=3757

Today I'm going to test fly my coaxial rotor system and see how she behaves.
Have a good day.

Bill