Also, if you want to toss heavy flies, then you need a leader designed
to do so. Furled, twined, or Singaporean leaders, as well as heavy
mono leaders will all do that if correctly designed.

For some applications "double tapered" leaders give superior results
for heavy flies. But a correct taper design will also work perfectly
well.

Using ordinary trout size/type leaders wont work for heavy flies,
regardless of how they are made.

TL
MC