Howdy, Doug. You're right, the compression damper adjustment will not help you in setting your race sag. You need to back off the adjusters at the top of the shock spring. The service manual calls out a special tool to grip the adjusters, but I've normally just used a long drift punch & a big hammer to turn the adjusters.
I had the rear suspension apart yesterday for the semi-annual clean & grease, and installed a 4.8 spring while I was in there. That required resetting the sag. I finally was able to accomplish what others have done, and that is grip the spring with a rag and turn the entire spring assembly. The upper adjuster will turn with the spring, making the job go faster. Taking off the shock mud flap provides better access to get two hands on the spring.
Good luck.
BTW, have you done the initial grease service on the rear suspension links?