The cutting or sanding part is actually for the snap on area of the lens cover ya?
Have to file the cap down, so that you can just plopped it on and off easily without pushing it hard it to snap it into place.
The next thing is to find an aesthetically nice item to replace the black foam tapes to prevent the vignetting...
Well, that guy I mentioned sanding the lens cover in order to reduce its thickness. So that the vignetting problem can be avoided...
I think the thing in your pic is some kind of rubber spacing piece... look nice, but how could it be fixed on the cover? glue?
If it's not very convenient to put it on then I think I will go with the 680 package without LC1...