re. heavy duty rear shock settings 500# load

[HDKLR@aol.com]

I am installing a new rear shock (dual sport) with 500/560 spring (Fred) on my A-6 after 11k mi. 4k with me (425#)+gear. Yes 450 pounds constant load. I am thinking of preloading new spring 1/2 in. Has any of you high load guys ever bottemed a 500/560 spring? Anyone know stock spring rate? HDKLR@...