Get these girder plugs. get string, tie to plug to one end and the fob on the other end of string(strong string). Leave key in girder cavity. Or just keep the key on you??
Forgot to tell you...when doing the mount, I ground the back of it(side that sits up against the plastic housing) round so it sits nice and flush against it. I guess can leave it square but not sure how far out it will be or how secure the fit will be. I rounded it out so it does not move at all...