ultra airshock jolts pillion spine and causes tongue biting (",)

[pielkop]

hi . 2014 ultra ltd standard airshock . 2 largish people with luggage pumped at around 46 to 48 psi. on highway etc very smooth and no issues but minute we hit secondary roads not in pristine condition (read bumpy) my wife is bounced up and down with shocks to spine etc. how can i rectify , is pressure too high , too low or must i look for after market shock..if so plse cvan you recommend a make etc.
thanks in advance