Springs?

anyone know of some stiff springs that will work on my LSP?
I tried the blue ones that came w/ it, and weren't stiff enough, so bought these: http://www.amainhobbies.com/product_...ducts_id/12692

they're about as stiff as the blue stock springs.. I've got 3 big clips on the shocks to keep the chassis off the ground :030:

I'm guessing my truck's around 11lbs. what do you guys use on the heavier trucks?