Braveheart,
You can add a turret via the DP file, but I don't know of any B-17 top turrets available as a weapon.
This approach was used with the Soviet version (Li2-See screen shot below) of the DC 3 using the stock MS C-47. The turret was designed as a weapon and then placed onto the plane via the DP file. Paul Rebuffat was the author of the plane. I don't know if it is still available, but a search for 2Li2Tv1.zip or the author's name might find it.
Views for airplanes are found in the panel.cfg file in the panel folder. Here is an example for a B-24D for the stock MS bomber. You can copy and paste this data into your panel.cfg file.
[Window Titles]
Window00=Main
Window01=Throttle_Panel
Window02=Bomb_Sight
Window03=Gage_panel
Window04=Nav_Panel
Fixed Window33=Rear
Fixed Window34=Rear Left Up
Fixed Window35=Forward Left Up
Fixed Window36=Forward Right Up
Fixed Window39=Rear Up
Fixed Window40=Rear Left
Fixed Window41=Rear Right
[VIEWS]
VIEW_FORWARD_WINDOWS=MAIN_PANEL
VIEW_FORWARD_ZOOM=0.5
VIEW_FORWARD_RIGHT_UP_WINDOWS=36
VIEW_FORWARD_RIGHT_UP_EYE=0.659,-1.567,3.9 // Chin Gunner left/right down/up back/forward
VIEW_FORWARD_RIGHT_UP_DIR=0,0,0
VIEW_FORWARD_LEFT_UP_WINDOWS=35
VIEW_FORWARD_LEFT_UP_EYE=-0.12,-1.18,2.69 // Front Left Gunner
VIEW_FORWARD_LEFT_UP_DIR=0,0,325
VIEW_REAR_RIGHT_UP_WINDOWS=42
VIEW_REAR_RIGHT_UP_EYE=0.45,-1.29,4.1 //LOW LEVEL BOMBSIGHT
VIEW_REAR_RIGHT_UP_DIR=10.25,0,0
VIEW_REAR_WINDOWS=33
VIEW_REAR_EYE=0.41,0.1,-16.0 // Tail Gunner
VIEW_REAR_DIR=180,180,0
VIEW_DOWN_WINDOWS=38
VIEW_DOWN_EYE=0.00, -2.90, -2.2 // Norton Bombsight
VIEW_DOWN_DIR=50.0, 0.0, 0.0
VIEW_DOWN_ZOOM=1.00
VIEW_REAR_UP_WINDOWS=39
VIEW_REAR_UP_EYE=0.45,0.60,-1.55 // Top Turret
VIEW_REAR_UP_DIR=180,180,0
VIEW_REAR_LEFT_WINDOWS=40
VIEW_REAR_LEFT_EYE=-0.10,-0.43,-10.22 //Left Waste Gunner
VIEW_REAR_LEFT_DIR=180,180,90
VIEW_REAR_RIGHT_WINDOWS=41
VIEW_REAR_RIGHT_EYE=1.0,-0.43,-10.22 //Right Waste Gunner
VIEW_REAR_RIGHT_DIR=180,180,270
VIEW_REAR_LEFT_UP_WINDOWS=34
VIEW_REAR_LEFT_UP_EYE=0.45,-2.80,-9.2 //Lower Ball Gunner
VIEW_REAR_LEFT_UP_DIR=180,180,0
Soviet Li 2 by Rebuffet: