As a general rule, as in a rule of thumb, not etched in stone...as the CORRECTED DA goes up by 2000 feet, you can go 1 range hotter plug, add 3-4 degrees of timing and go down 2 sizes in main jet. For 1000 foot moves I usually just add timing.
If your base tune up is close, this works pretty well. If you are on the fat side of max HP, you will see bigger losses in ET and MPH with lower weather changes. In other words, if you are running rich and your CORRECTED DA was say, 500 feet (I've seen conditions at DP go 600-700 feet BELOW sea level) and you show up and it's 2000 feet, you will have to make some big moves to keep up with the power loss.
No matter what, when the DA goes up, you will lose power. The trick is to not lose as much power. Kinsler used to have a bunch of math posted on that web site for the nerds among us.
Most guys now have weather stations that tell them how much to move the throttle stop to compensate for DA changes.
