Spring Fever!

I'm trying to select the correct secondary spring for my sled. Those of you who read the posts in "Primary Clutch" from wednesday know the issues related to galling of the primary sheaves. In order to prevent my secondary from opening prematurely I need a higher final force. This is where the guessing begins. Stock final is 300, other options are 315, 325, 350. The kicker is that the inital rates are also much higher, which i've been told is good to a point for backshift. The 600 is strong with several mods, but how much inital is too much? HELP....