Replacement feeder head for Stihl FS45

I have the residential FS45 trimmer that came with the "AutoCut" "tap" version. It's always been crap, and has never worked right. I finally lost the spring for it, so I need a new head. I was set on the AutoCut C-25-2 which has the "EasySpool" function, but I also read that it's pretty bad.

This led me to find the "SpeedHead 450" heads, but I'm still not sure if they are compatible with my FS45 (which has a slightly curved shaft). Does anyone know if it will work? If not, do you have...

Replacement feeder head for Stihl FS45