extremely soft 2nd to 3rd shift

I agree with the suggestion that you should take it back to your rebuilder. It's under warranty & by you messing with adjustments you may void the warranty. I can tell you in my shop if anybody goes inside a component, i.e. Transmission or engine or whatever, we rebuilt or installed the warranty is void. Even the cable adjustments should be made by their trans tech. Play it safe, leave it to the pros & protect your warranty.