Thanks for the heads up on the Airfix vs Italieri kits. Maybe I'll wait until I can find the latter then.
Interesting comparison, a friend of mine is building a Flower Class Corvette, also 1:72 scale like the U-boat. The two models, same scale, are just about equal in length to each other. But the difference in hull size is considerable. The corvette is so much beamier than the sub that you could almost put 4 U-boats inside the corvette, stacked like 4 torpedo tubes.
Seeing the two together is what got me thinking about a Schnellboot companion to the U-boat.