I never thought of using crystal. But you just gave me an idea - I've been turning colored acrylic lately and a sky blue clapper might be a nice surprise inside!
I have always made them out of wood, fairly lightweight, suspended with a piece of wire. Some people have mentioned they glue in a piece of fishing line but I haven't tried that. This is one that was broken on a trip so I cut it in half to show the construction:
bells_cutaway_IMG_5169.jpg
A 1/8"- pierced wall would give me fragility worries!
Again, I admire your beautiful work of art.
JKJ