On two unrelated video clips from European anglers I viewed recently they tied their fly to the tippet with a novel variation of a Clinch knot.
They used a basic clinch knot (not improved) but tied a simple overhand knot at the end of the tippet to prevent it from slipping out.
Is this an accepted variation? 
Ray,
Several schools of thought about tippet to fly knots. As far as I know, there are no āacceptedā norms.
Some feel that faster (or perhaps āeasierā), even though weaker, is best, and you get the clinch knot folks and the other āquickā knots.
Some prefer stronger knots (there are lots of those out there, most are more difficult or take longer to tie).
In my albeit non scientific testing, adding an overhand knot to a clinch knot does not make it less likely to slip or cause it to be any stronger. Doing the improved clinch knot does add strength. Though itās still not a very strong knot, going the āimprovedā route will give you more results than adding the overhand knot will.
Up to you, of course. What knot a fisherman uses is intensely personal.
Buddy
Improved clinch always works for me. I can remember how to tie it, it always worked for bait and spinners. Never lost a fish from it that I know of.
the application of specific knots are really of personal choices. Iāve noticed that over the years Iāve learned to tie different knots to hooks because I canāt see as well or Iām using larger flies (for the same reason). My favorite knots for attaching leader to fly are: clinch(reg), Orvis, and Davy Wotton
Over a period of years Iāve found a couple type of knots that have worked very well, that I can tie easily/fast and that maybe Iāve perfected a tad, too. The old standby clinch and for streamers a closed loop.
I think tying a knot consistently well is important ā a ābetterā knot tied poorly is a bad knot. So I stick with the improved clinch knot. After years of practice, yes, I can tie it faster, but more importantly I can tie it consistently well.
Ditto that!
Thanks for the comments but I guess nobody has really familiar with the variation I saw in the European clips.
Ray,
That was the first mono knot I ever tied. My uncle taught me that knot with an extra not at end. We later switched to the improved one.
Bob9
Ray, Lots of us do things that are based on ālocal wisdomā. I think the clinch knot with a square knot on the tag end is one of those. Adios Philip
The best tippet-to-fly knot is one that can be tied accurately, with cold fingers, in the dark. While the improved clinch knot may not be the strongest knot out there, itās one that I can tie, quickly and correctly, without having to think about it.