crazy story [printed a hook to hand bikes]

[printbus]

Yeah, I think you'd be wasting your time trying to add metal to the print. Could actually be weaker in some ways since the printed material won't bond very well to the metal. This is the point where you go to the hardware store and buy what they have instead. It'll be money well spent and you won't keep checking to see if the bikes have fallen yet.

That said, here are my comments, beyond what Talon suggested. For starters, I think it's a weak design for what you're wanting it to do. I couldn't quickly find an example of what I'd suggest, but I think the wall facing part of the hook should have extended down a ways below the bottom of the curve, with something like a reverse arch carrying load from the bottom of the curve into the wall. This is NOT what I mean, but at least this item on thingiverse seems beefier than the one you printed: http://www.thingiverse.com/thing:1014663

Your hex infill has the most strength 90 degrees from how you need it, which is not easy to fix with the print orientation you're pretty much stuck with. A simple criss-cross infill like rectilinear would possibly be a better choice. I would have went with 80% or so infill, shooting for a print that was almost solid. And I'd have likely went with double the perimeters and top/bottom solid layers from what you have.

EDIT: But I still don't know that I would have trusted it.

EDIT #2: This isn't a wall mount hook, but the shape of the curved part reflects what I was trying to describe. Note the reinforcement under the hook. http://www.thingiverse.com/thing:1195175