I don’t have an official correct hcp at the moment but my garmin has me at 18,8. And if I see correctly it’s still a greenside bunker so the shot should be closer to 20 yards not 40? My bunker play is definitely better than my hcp would indicate. It very rarely happens that I don’t finish on the green from any greenside bunker shot. And a majority of the time I’m in easy 2 putt range.
I'm not quite sure this makes sense. Just because one shaft feels better on a certain club doesn't mean that it will feel just as good on a different club. I think a range session is in order for you, but I don't think that having a shaft longer than stock (assuming that you are of normal height), will be any kind of positive on that club. That's more of a long drive mentality.
Side note: swing weights are a thing, and if you mess with them, they can mess with you.