Fan cover

Every stormy winter day, the exhaust fan on my bathroom starts rotating powered by the wind outside. Not sure if its cold air pulled in or hot air pushed out (probably both) but we can see the fan rotating (while unpowered) and feel some discomfort as the bathroom temperatures are a bit reduced.
The solution has been to cover most of the fan with tape, to limit the flow. Problem solved.
This year, armed with a 3D printer, I decided to make a solution that could be easily removable. The main decisions were how to fix it (fan is on the ceiling) and how much to cover it and still allow bath moisture to be removed.
The original idea was to use some clicks/hooks to hold the cover and open a hole under the fan rotor to allow dismounting. During the modelling, I had the idea to slightly bend the cover struts to produce some friction.
I made a first print and... Bingo!!!! It fitted like a glove!
This was one of the rare occasions that it works so well that I was not even tempted to make small