I was fortunate enough to have a good look round both the B-17 and B-29 at Houston during an 'airsho' once. The B-17 seemed much more primitive inside and would have been pretty cramped in the flight deck area with an upper turret fitted. Whereas the B-29 was more spacious, but I didn't try the crawlway! There was an interesting chart in the gunners' area which was an aid to diagnosing engine faults by the colour and volume of smoke! Was it a fire, supercharger failure, oil leak or what? The rear gunner's position in the B-17 was pretty tight, but must have been really tight for someone dressed in full flying kit!
The CAF were kind enough to allow me on board 'Fifi' during the engine starting sequence and would have taken me flying, but this wasn't long after the B-26 accident.
B-17 or B-29? Actually, for me it's the B-36! Before the jets were added, that is. A really huge aeroplane; Revell made a 1/72nd scale model of it and even that had a 38" wingspan!