I use 3 high tension springs. i cant use 3 normal springs, as with 10-59 i have to screw my claws in all the way in e, and i tune down half a step with a 10-68. Youll get better flutter with fewer springs stretched more than you will with more springs stretched less. also, screw the treble side in more than the bass side. sounds crazy, but ive done it to my carvin and cameron (here, supertruper1988 at ss.org) or aaron at ss.org can tell you from saturday's meetup, that trem flutters like pretty much no trem ive ever seen (short of my coworkers sg melody maker lol).
Ive done it on my RG350 since then and it works amazing.
edit: i got them from rich harris, btw
i dont like dealing with him lol (his policies with payment, while understandable, suck to deal with), im trying to find somewhere else to get some, as i need some. i bought a whole stash of them about a year and a half ago and im out.
If you find any other sources let me know. Gotoh makes them, but my shops not a gotoh dealer
edit 2: the "standard springs are 52mm long. the high tension ones are 47mm. the fender black springs are 52-53mm depending, and just use springs with a higher k value.