Linear actuator using geared retract motor.

I designed parts to make an actuator from these geared retract motor units I have.

This is the motor unit I used:
http://www.ebay.com/itm/Worm-Motor-Control-Board-for-Retractable-Electric-Landing-Gear-/172104935631

EDIT:
After playing with it for a while I noticed that they will reverse if they are blocked or if the channel is flipped when they are unpowered. I bought my motor units six months ago, so this issue may be fixed now, but for now I can't recommend buying these motors unless