Max skill enchant rate depends on your character's level. If you have extended your max level to 85 or something you should edit EnchantSkillNode in order to avoid IOOBE and parse new values to your set aswell (rate81 rate82, etc). As for the max skill enchant value, acis already handles up to 30, both in skill and enchant skill xmls. All you have to do is manually increase values in enchantskills.xml (rate76 rate77 etc) for each skill level. If though you would like to extend max enchant to 31 you will also have to add extra lines to enchantskills.xml, increase enchantlevels1/2/... AND extend tables like #ench1Power in order to fit your new max enchant level.