I have no problems with a clinch knot and flouro, both in salt and fresh. I moisten it, and pull it tight slowly, and then put pretty good pressure on it to tighten it down. No sharp tugging pressure, but a slow steady pressure. I believe as Chromedome said, it all about tying it properly.
If you read Chico Fernandez's book Fly Fishing for Bonefish, when not using a loop to attach the fly, he uses an 7 or 8 turn clinch knot, and he has tested it against an improved clinch and with 8 turns it came out stronger. A simple clinch knot is all you need if tied properly. He says an 8 turn clinch tests at 99-100%.
Cattaraugus Creek Outfitters
God does not deduct from man's alloted time the hours spent fishing.