Front fans for a Fractal R4 design case

I just received 2 120mm Noiseblocker fans in the mail, but they don't quite snap into where the old 140mm Fractal fan used to be since it's smaller. Is there a best way on how to keep it securely fastened to the front fan bracket?

Zip ties, Velcro, ingenuity?

Yeah it doesn't really matter, they don't have to screws they can just be jury rigged into place.

Same with hard drives, they don't really need to be screwed in either, as long as you don't move your full tower 75lbs computer when its on...