Spacers = fps
St bolt = efficiency, "smoothness" .., and keeps the ball / reball mainly to get stuck in the bolt tip (open bolt + small reballs..)
My geo1 worked perfect without the spacers and the st bolt on reballs.
I got the gst kit, and noticed a difference in the above properties. Efficiency is not the geo1 strong side, so every measure that helps on that is beneficial.
There are many threads on this in this forum. But i recommend you to try yourself first. And i recommend you to get a gst kit cheap somewhere