You may want to give fused claptons a shot. After noticing the same as you in regards to simple-round vs. single-core claptons,
fused is where it really did get much better.. Surprising me in the process.
Interesting about you wanting to try rayon.. Whenever I get cotton samples, I can't wait to finish them and get back to rayon. Afterall, I'm way too cheap to just want to waste it by throwing it away.
Also interesting about the talk of wrapping thicker gauge around thinner. I hope to try that at some point with one or two strands of 34g ni-200, wrapped with maybe 28g ni-200. If nothing else, at least help get rid of 1,100ft of 28g ni-200 that I mistakenly stockpiled on. ...Or maybe two 32g kanthals wrapped with 28g ni-200.