Greenhouse roof braces V2

To have optimal use of your greenhouse it is wise to block the sunlight from the roof. This can be done by painting the glass of the roof white, but in the fall you need extra sunlight and removing paint will be a big task. I have tried several thing like using a bed sheet, but due to the moister in the greenhouse, this sheet can not be used very long. So my next trail is to use styrofoam sheets of 1 cm think. (very inexpensive material). To hold it in place I created braces to hold them in plac