Can I leave over tightened headless screw in ss band?

Installing PE water line and after struggling for hours to make the connections (deep deep narrow wet hole!) I over tightened one of the ss bands securing the male brass fitting in PE pipe and the screw head came off. I am thinking its ok to leave it as its obviously tight and the head us only for removal. So ok to leave it? (Asking on off chance it can somehow loosen up)

You can leave it, just add another clamp right next to it for insurance.

How tight?

Is 60lbs/in^2 such as provided by a cast iron pipe torque wrench a good amount of tightness for these bands around PE? Any thoughts?

If the head broke off, if you tap it with a hammer it will likely let loose altogether. You were WAY beyond normal torque or you have some fine chinese junk. If you warm the pipe to about 200F with hot water then the clamps can be tightened with a little screwdriver or a 1/4" socket wrench until snug. Recheck in an hour.

An SAE 56 clamp takes 45 foot pounds.

http://www.grainger.com/Grainger/IDEAL-Hose-Clamp-1XHB3?Pid=search

Here is a USA clamp for 30 foot pounds.

http://www.grainger.com/Grainger/IDEAL-Hose-Clamp-2PA63?Pid=search

And marine grade, a good investment

http://www.grainger.com/Grainger/IDEAL-Hose-Clamp-1XHB9?Pid=search

End Result

In the end, I did hit the thing with a hammer and it did not budge. It was the first band on the fitting, so I moved the second band even closer to it and added a third and called it a day. Thanks for your replies.