Well THe only thing that I can tell you is when I did my 4 inch lift on my YJ is I had to do a one inch transfer case Drop, and I am not useing a SYE Kit and it works Just fine, No Broken U Joints Yet, But it may be different on an XJ.
On My transfer drop I Used one inch Square tubing and It works great.
Al
PS I also Had to use I Beleive it was 3 degree Axle Shims on the rear Axle