Modding help with side panel

[Bazyks]

How would you guys close this gap?i put an acrylic window and it isn't a tight fit.Would leaving it like this affect dust filtrering?

https://imgur.com/a/DAc0QZo

 

[RememberThe5th]

I think putting an foam/sponge type glued acrylic window should be pretty?

 

[Gam3r01]

You probably should have bought the correct size piece of material in the first place.