I recommend that you leave off the cover and detail the sight.
You appear to be spending a bunch of time, effort, and money on this project so make it an operationally deployed vehicle equipped and fitted the way it would be in combat...i.e. leave off the sight cover. The sight would look very nice with PE details and the optics.
The sight is a stand out detail on the 2A6M turret so you should show it off.