Outer Limits 4x4 Board

I'm about to put new bushes in my rear arms as they are worn out, while i have them out i'm thinking about makeing them more stronger by replacing the pipe with a thicker bit and a touch longer "16mm",to get the pinion angle back to normal because i have 6inch springs. My question is would 16mm longer than standard be the right measurement and do i have to do any thing to the upper tralling arms like shorten or lenghthen them?

On my 4inch lifted gq I sleeved the lower rear arms, made them 16mm longer and left the uppers alone, seems to be working fine for me.

But not sure with regard to your 6 inch lift