I am close to pulling the trigger on a 500mm F/4G lens. I found a second hand one in good shape. Any advice from users of that lens would be helpful. I know they are heavy but can they be used hand held some?A new 5.6 PF is more expensive but much lighter. I also found a 500mm F/4 D ii. They are even heavier but cheaper and no VR and not sure how long they will be serviced by Nikon.. Thanks