Another piece to preventing cracks is not rushing, take your time to kit up and equally take your time getting dekit. The number of times I have seen damage happen taking a kit off is not one, so be careful....
I ONLY use hard crates for armour and even them am careful with how its handled.
Like others have said reinforce the shoulder straps (and be careful with them when packing/unpacking, and reinforce your edges where you can....