I recently installed a frameless sliding shower door. The bottom rail was placed on a strip of stone ( 3" wide by 5 ft). The sliding doors etc are ok. The bottom rail is in place only by virtue of the two vertical pieces - so. although it is not going to come out, there is sme amount of "play".

Question: Is it recommended to glue aluminium to stone? ( Cannot use a screw as it will crack the 3" stone strip).

Silicone the track to the stone.