Using a heat gun to just heat the area that bends is what I usually do. I heat both sides and then bend the plastic over the edge of a sharp table or counter top. I suppose on such a small mold, it could be pretty hard to heat just the bend though.
Awesome idea for my next project, although I still have two more grow beds to build first.
I wish my cucumbers were doing as well as yours.
Trust God, after all, only He knows what He is doing.
Random Thoughts: There is some truth in every newspaper and magazine, you just need to know where to look....
For instance: The name, price, date, and page numbers are usually always true!