Let me reword my post, Bill.
Yes GLB's are strong, but they're sized site specifically for their job of holding up the roof. Any added weight and/or modification to them (drilling) must be sent to the structural engineer for approval.
Some people will look at their massive size, and figure that they can hold up anything, but it's just not true.
I've only seen a couple of them with holes bored through, and I'd imagine that these were done without approval.
