[Dad1279]

I think there are (legal) valves available that will allow positioning. Perhaps you can research that option, or someone else can chime in.

Since there are only a few set heights, will your design allow you to use multiple cylinders stacked to achieve the set heights?

Do you have additional Toughbox parts? You could stack 2 toughboxes, or make new plates and add additional gear reduction internally. Or use a small sprocket on the output to drive a larger sprocket. You will need to balance the arm or do something to prevent backdriving.

You could also use the output of the toughbox to turn a screw, which would further reduction, and convert to linear motion (to replace cylinder)

Another option, if you are not using them already, could be to use multiple window motors.