Two images I found on the net.

Here a cockpit image of a 109E


Note that the left edge of the reflector sight is on or at least very very close to the centre of the cockpit. Also note that the reflector glas is quite big.

Now here an image of a pilot sitting in a 109. Please note that he sits a bit leaned to his left side but it gives a good impression about where his eyes would be if he sat central:


I think the paralaxis is so small that my guess is that he wouldnt have had to lean sideways for aiming.