adding a leaf or two from another stock XJ pack works well and it doesn't make the ride rough. It is a little more firm, but definitely not rough.
one caveat: it is a PITA. If you are looking for easy, the Quadratec replacements would be a good bet.
'98 XJ: UpCountry, bastard pack, 2" spacers, JK shocks, 31" BFG AT's
'81 Honda GL500
Colorado Jeep Club Member #399