I have about 75,000 miles on my 3"/3" lifted rig with KDSS. No issues so far.
Big benefit of KDSS on a lifted rig is stability on road. If you top load your rig it can get pretty precarious on turns. (Also think existing load riding higher due to lift.)The extra sized sway bar and KDSS help a lot to counteract that.
3" is generally considered the high end for KDSS equipped rigs. However, the last link I referenced below would provide a solution allowing you to go long travel rear with KDSS. I might go down that path next.
see these threads for good info:
Let's talk about KDSS and sway bars
5th Gen. KDSS vs. Non-KDSS handling performance & sway bar diameter differences.
https://www.toyota-4runner.org/5th-...panhard-bar.html?highlight=kdss+rear+sway+bar
