Piesupper - delighted to have my brains picked (such of them that are left!).
The field of view from the periscope was quite narrow and you could only view one aircraft/hose at a time. With 2 in contact it took several seconds to motor the periscope from one to the other, somewhere between 5 and 10 seconds if memory serves. If you have a look at the V force reunion website
V-Force Reunion , click on 'Gallery' and go to the 5th page there are a couple of photos taken through the periscope by my old plotter Don Chadwick, and they will give you a good idea of the field of view.
The 6th seat was used by crew chiefs, and for "trappers" on check rides etc (and on one occasion a rather nice WRAF ATCO in Cyprus
) It was mounted on rails on the a/c centreline, aft of the pilots and forward of the rear crew. It could be mounted facing forward or aft, as the need arose, and was only carried when there was to be a 6th on board, as otherwise it just got in the way!
I was never on bombers and in 6 years on tankers never once heard of anyone going down in the prone bomb-aimer's position in flight. Some may have, but I certainly never did. Wasn't even aware that the glazing was removed but I only actually served on K1/K1a. BTW duty free etc that didnt need to remain pressurised usually went in Annie's hatch at the rear of the aircraft.
Feel free to ask if you need any more info, either on the forum or by PM - glad to help.
Dont know whether I'm speaking out of turn as a non-pilot (unless you count Cessna 172s) but re the JPT limiter, 101.5% power setting was available for max weight takeoffs etc, and this entailed a higher than normal JPT which was only permitted for a limited time. Normal JPT was 625 if memory serves but what temp was reached with the 101.5% setting I'd only be guessing (660?). Standing by to be flamed by someone who actually knows what they are talking about!