In real basic terms, Dave, although it's not sounding that bad currently and you can shoot okay with it, shortening the spring further will make it stiffer. Rather than more "solid preload" you want nice, soft, cushioning active coils. If you're happy with it as is, and it stays legal / not too close to the limit, persist and just get used to the gun. But shortening further wouldn't be the way to go and I'm sure you'll be much happier with the manners and cycle with a softer spring fitted in the long term.