40mm fan cover

I used to use a flat fan cover (yellow one on the pic). But, it's inevitably that i would hit my nipper into it,which might break (and i did) fan leaves.
I saw a similar design (the white one next to the yellow). It's for 50mm, so i made a drawing for 40mm. But, after using it, i found the semi-circle shape is a little big. And, there is still a chance that i might hit nipper into it.
So, i reduced the gap, and it's more beatiful. Now, it's perfect for me. Hope this would help someone.

3D