Paul, I went through the exact same thing with fluoro to mono connections. I tried every knot I could and nothing worked for me. Someone on here suggested the tiny metal rings that feaher-Craft sells and uses on the end of their braided leaders. I picked some up and tried them last year…problem solved.
For nymphing I have gone to using a butt section conisting of 18″ of 0X and 18″ of 1X. I put the ring on the end of the the one 1X and put a big loop in the other end that gets looped to a braid on my lines. I use corky type indicators. When I want to take off/put on the corky I take the leader off at the loop. I setup three leaders in September, one for nymphing with each of the two reels I use for Steelhead and one one with a fluoro tapered leader from feather-Craft for streamers. Each has a metal ring and I am still using the original three rings. I adjust the entire thing with tippet and when using an indicator I have 36″ of adjustment room on the leader itself. Simple, fast and it works well for me, casting just fine out to any distance I can reasonably fish. The 0 and 1X are thin and sink faster than a more traditional leader formula, which I have found to not be needed. Keep it simple…
Hope that helps
Steve