I tried about 10 times using 300/300/400/500 as the guy a few comments above said, using a light carrier as a flagship and built them both. Sounds like a decent number of attempts but for a relatively low resource consuming recipe, it's worth it
Use RJ kai2 as FS with 300/300/400/500 and get both in relatively short times and tries. (less than 20) Along the way I got Kaga, Shouryuu, and Hiryuu along the way. While the 3 are all dupes, it seems like it's a very reliable recipe to get CV.
To everyone who got Shoukaku one way or another through the recipes...
What did you eat? Did you bathe yourself in salt water? Did you make a summoning circle?
Because look, over 70 tries later I still did not get her.
I even tried to farm for her at 5-1 (wiki page says it has the highest drop rate at 1.81%), and over 50 tries later I accidentally sunk my L95 Yuudachi trying to get her (and failed miserably)
Being an admiral without Shoukaku for over 2 years is just too much, I can't unlock the quest chain and I can't get some of the better planes. Maybe I'll just hope that posting here will do some miracle for me.