To simplify the installation a T bar should be made. It will make the layout much easier and it will hold up the cross arm. This will save you from working against the spring tension.
Make the T bar from 3/8" rod, make it to fit the largest hatch opening of the bins you are going to install openers on.
Put the leg of the T bar through the back rail hole and center the to of the T bar with the center of the hole
Mark the holes for the back rails as per the individual instruction.

After the cross arm and springs have been installed you can put the T bar under the cross arm to hold the cross arm up.

1. Layout holes for side brackets and back rail with T bar
2. Drill pilot holes with tech screws and drill 3/8 holes
3. Bolt back rail to back rail bracket withwasher,spring ans eyebolt already on it.
4. Install back rail and side brackets with 3/8 bolts
5. Slide springs onto cross arm and install into side brackets
6. Drill two holes on the lid and secure tower.
7. Put the eyebolt on the rail through the tower and secure
8. Attach springs and elevate arm with T bar.
9. Turn nuts down on the eye bolts and put them through the lid using 3/8 washers top and bottom. Secure with nut on top
10. Make a loop in the cable with a cable clamp and secure it to the lid with a bolt and 3/8 washer.
11. Tech screw the back rail to the roof sheet being carefully not to strip the threads.
12. Remove old lid cradle if necessary, check for smooth operation before descending .
13. Tech screw chain bracket to the bin wall at a comfortable height.
14. Tech screw chain to chain bracket with 1/4 washer.
15. Cut and secure cable to the end of the chain with a cable clamp