Oh, there's a movement switch, I missed that detail. I agree with Craig, just do some dots. I would steer clear of liquid glue, it has bad news written all over it!
I have a 1680 too and the CG is something I'm having trouble with too... When I get mine back, I'm going to post pictures and see what the experts say. I think it's all in the quality and angles of pictures you can take. Many online are very difficult to see...
With that kind of watch, as long as it keeps good time! Besides, it's not a grail... people are going to see it and say "Rolex", not "that crystal looks funny!"