Yes, should be OK, just make sure you don't remove too much material when modifying the aperture.
Also be aware that you can't remove the 8" screen without removing the vent assembly.
There is a stepped line on the top and bottom of the frame i just used a multi too with a saw attachment to lop them both off needed to cut the clips that sit behind that line a bit too for the screen to sit flush. looks like the 4 fixing points are the only thing holding the screen in so yes the old screen should go back in ok, Shame you lose 4 fixing points for the trim though so the middle is very slightly loose when touching the trim.
The vent that comes with the 8" screen could be modified but far more work, the original one is angled on the right side fixing point why they changed that god knows.
