Most instructions I've read of how to tie a clinch knot, or even an "improved" clinch knot, don't include tying a square knot on the tag end.  I've found that snugging the square knot against the main knot prevents any possibility that the tag end will slip through, so that the knot doesn't fail when you need it most.

 

Thoughts?

I don't see what it would hurt.  I never liked the clinch knot for that reason, I always used a trilene knot instead up until a few months ago when I discovered the Pitzen knot.  Very easy, very secure, and I think it''s a tidier knot than either clinch knot or the trilene knot.  Just a suggestion.

I used to do that with more expensive lures, and I never had any problems. I could see it preventing a slip, but I haven't had it break on me with the square knot after the clinch.

 Square knot wouldn't hurt.  Singeing the tag end with a bic puts a little nib on the end, does help preventing pull thru.  When it comes to a knot for braid I use an improved clinch, no problems, that said when I'm targeting fish like snook and tarpon, still only use 15 or 20# lines I make a second wrap on the improved clinch.  Whatever your knot preference is, just tie right and there should be no problems.

A fish pulling out line seldom breaks the line or a knot, it's too tight a drag that cause problems.