It's going to heat up like ya read about. Black plastic+ sunlight= quite hot.
If you made it so that the whole thing sat over the plant like a bell, you could porbably force-flower a single plant under there by covering the plant at exactly the same time each day and removing the cover every morning, like cover at 6pm and remove at 6am.
Or you could grow an autoflowering strain and save yourself the worry of an alarm clock.