I just use some of the John Guest gas line as it is reasonably stiff. I have no issues with coiling etc.
I'm not sure that boiling the stone in wort would be a great idea. I've always tried to ensure I have had O2 running through it before submersing in any liquid to prevent blockage of the 2um pores. I imagine if it were suberged in wort for 5 minutes, there is a lot of material that may cause blockages.
I simply turn on the O2, dunk in starsan for about 10 seconds, put into the wort to do its thing, remove and place in the starsan for another 10 seconds, take it out and turn off the O2.
So far works for me.