Thanks for all the replies, guys. It should be obvious to you all that I am not experienced with these modern guns re. tuning and such, so I am going to see where this experiment takes me just for the experience, I need to see it for myself...but I will be ordering a more suitable spring and will probably be asking more questions as and when.

Just a footnote, what if I reduced the stroke with say one of Tinbums short stroke kits and kept this spring as is?...wouldn't this add preload and reduce the potential energy within the set up?

ATB,
Dave