star lsw spring length?

[skapunkninja]

Morning all.
I got a star sa80 LSW as part of a trade, and want to get the fps Upto 350ish.

The gearbox is quite abit longer than a standard box, so an m110 spring just drops in without needing to be compressed at all, and therefore only puts out about 280fps.
Anyone upgraded one? What spring make/rating did you use?