Inner blackout tarp help

Hello everyone,

This is my first time posting anything on here but here it goes. I am having some trouble trying to figure out how construct a inner black out system for a greenhouse I'm working on. What I've figured out so far is that there are a few options to tinker with. There is pulley and cranks that attach every so many feet. There is making an inner skeleton using wires and beams. If anyone has some other or better ideas I would love to hear them.

Forgot to give the specs. It is a 30x72 the peak is at 17' but the truss braces are at 14'
This is how it looks on the inside with the vent

Use or get inspired by automated wire systems. check them out and you know what to do.

If you will have fans inside the grow area blowing at dark out the cover might move so think about a solution for that.

You can get a simple motor that is designed for that specific use if you do that you can automate the process.

The greenhouse industry have used these systems for a very long time so you might be able to find something second hand and go from that or even better build a greenhouse that fits it =)