Follow up question: I remember reading that school boys in metal shop classes were put to work manufacturing Stens in WWII. Is there any accuracy to that at all?

The Sten, Sterling Owen, Austen, etc., were designed with the input from the users. The main reason was that, if a 32/34 round was located under the weapon, the firers' head would be raised when firing aimed shots from the prone position.

It's a design feature that works very well, it makes perfect sense to anyone that has used one.

The BAR only had a 20-round mag below the weapon; the Bren designers almost certainly studied the BAR whilst producing their design.

The Sten should never be held by the mag; it would cause stoppages. The mag was the most fragile part of the weapon system and were often a loose fit in the housing. The parts were made in dozens of engineering workshops and the tolerances were large. The Sterling had much better mags and was far better made, you could hold one by the mag or mag housing without causing a stoppage. You might accidentally press the mag release catch, so it wasn't approved. The perforated barrel shroud is where you were meant to hold it.