The 17s had a service altitude of around 35,000 feet - about the same cruise altitude as a modern airliner, but without the pressure body. Most missions were flown between 20,000 and 30,000 feet - from 3.7 to about 5.6 miles up - unpressurized. Go read Flying Fortress by Jablonski, and look how far away the ground is on those low altitude missions.
Even if they caused a sudden depressurization that would be no big deal.
No big deal to who?
I won't appeal to any authority except documented, web-linked facts, which should be a relief in this thread.
It's a commonly accepted figure that airliners are generally pressurized to about 8,000 feet altitude or less, or an internal pressure of 22.22 inches of mercury, or 10.9 psi.
Flying at the usual 35,000 feet, the outside air pressure is about 7.04 inches of mercury, or 3.5 psi.
This means that the pressure differential between the inside and outside of the plane is 7.4 psi, and according to page 6 of this document, the outflow valve has a maximum cabin pressure to outside pressure differential of 8.6psi, and the cabin air is completely exchanged for outside air (even including recirculation) around 12.5 times per hour, and at cruise, the lowest pressure bleed on the engine's turbine produces 30psi.
For comparison's sake, 7.4psi is around the low end of the typical inflation pressure of a basketball. Now, looking at this page containing the mechanical property data for various aluminum alloys, the lowest yield strength (force above which material is permanently deformed) is 5,000 psi for 1/2" sample.
Aluminum honeycomb, a common component of airplanes these days, has a transverse plate shear strength of 65.3psi at a 19mm cell size and 0.064mm wall thickness, and higher for smaller cell sizes.
So basically, what you're saying when you say that there could be a James Bond, suck-you-out-of-the-plane scenario if a .45 caliber bullet penetrated a pressurized fuselage, is that air leaking through that hole at a 7.4 psi pressure differential would develop enough force on the aluminum plate and honeycomb materials surrounding the hole to overcome a minimum of 65.3psi transverse plate shear strength.
Leaving all this aside, there's plenty of bullets available that won't penetrate an airplane fuselage unless fired directly at close range - Glasers, to name one - making this whole discussion utterly moot.
The most famous example of explosive decompression in an airliner was the 1950's era Comet, which split open like a ripe tomato due to metal fatigue, not a half-inch round hole.
In 1988, a 36 centimeter (14.1 inch) hole in the fuselage of an airplane at 31,000 feet resulted in ZERO fatalities and a safe landing. In 1986, a passenger detonated a GRENADE in a rear lavatory at 33,000 feet, causing depressurization, and again ZERO fatalities and a safe landing.
And you're worried about a 9mm or .45" hole in the plane? Come on.