After finding the information on the DO-217B Periscope & how with the aid of it's mirrors gave the pilot the illusion while looking through it he was looking forward at his target.
I think this is how the views would have looked some what from the pilots perspective if he had rear guns to shoot with on the B model & most likely the view from the C model.
In this thread
http://bbs.hitechcreations.com/smf/index.php/topic,305406.0.html All evidence of rear pointing guns on the AR-234'S shows it was rearward facing & downward.
From the blueprint drawings I think it was somewhere at about one & a half to approximately two & a half degrees.
Interestingly it is about the same angle as our AHII AR-234-B guns except in game ours are upward facing.
So the pilots knew the angle of their rear guns & all the views they would have looking through that periscope. I would assume they would have had there cross hairs on the sites set at a specific range based off what they would have seen & the 20mm ballistics.
All the AR-234-B's made I think would have had a rearview through the periscope like this below. There was no need for a forward shooting view through the periscope since he was not shooting with rearward guns very similar to the ME-110 Periscope view. The only thing he needed to know was there some one behind him & where.
I had a squadmate put his Mosquito XVI in a position that most likely the AR-234 pilot would need to have to shoot at an enemy. In this case the plane is at 600 yards away.
Now imagine one eye is closed the other is on the periscope & now this is what you will see as your new forward view to track & shoot an aircraft just as you would in any conventional fighter.
Or there abouts.
I would say if rear guns were ever to be used pilots would try & avoid at all costs getting in a situation to have to use them.
234 pilots would always have to be higher & ahead of the target to get a firing solution I think this was enough of a reason just to do away with them all together.
Why not no allied plane could catch them at full speed.