case SM_BASH:
if( sd && skill_lv > 5 && pc_checkskill(sd,SM_FATALBLOW)>0 ){
//BaseChance gets multiplied with BaseLevel/50.0; 500/50 simplifies to 10 [Playtester]
status_change_start(src,bl,SC_STUN,(skill_lv-5)*sd->status.base_level*10,
skill_lv,0,0,0,skill_get_time2(skill_id,skill_lv),SCSTART_NONE);
}
break;
Stun % starts at level 6 so in this line: status_change_start(src,bl,SC_STUN,(skill_lv-5)*sd->status.base_level*10,
on skill_lv-5 means 5% when you have bash lvl 6, if lvl 7 bash stun chance increases to 10%...
and base_level has a aditional chance to stun.
So you need change skill_lv-5 to skill_lv-10 that means every level you have 10% aditional chance.