By the way, I have had some good suggestions of other actuators in this thread: Skid Steer Mower Overshooting pivot turns
Skid Steer Mower Overshooting pivot turns
I have bought a lead screw, a 10-turn pot, and a cheap cordless drill (2 of each). I plan to try to make an actuator out of these. But, if I had not already bought these, I would try some of the suggestions from others. The little linear actuators I have are hanging in there right now.