A true 20+ generation project is almost unheard of as far as I'm concerned. That would be 10+ years if your breeding all season every year.
I understand its often said it is a 10 year project to create a new breed that breeds true but not many actually follow through with a project that long...
Frizzled crossed with smooth gives you 50% frizzled and 50% smooth.
Frizzled crossed with silkie gives you 50% frizzled and 50% smooth.
Silkie crossed with smooth gives you 100% smooth.
F20+?
It shouldn't take anyone 20 generations to get a frizzled sizzle.
I would think you could do just about...