Yes, they only work when the plane is in an upright position and the wing lift is "pulling" the wing upward pulling on the struts. If the plane is being flown inverted then these floppy struts do nothing in compression to reinforce the wing. I have been told that the wing can fail if flown inverted with the stock struts. Don't know if that is true or not as I reinforced mine with bamboo skewers from the get go.