function midcast(spell)
if spell.skill == 'Elemental Magic' and spell.element == world.day_element or spell.element == world.weather_element then
equip(sets.Nuke, {waist="Hachirin-no-Obi"})
elseif spell.skill == 'Elemental Magic' then
equip(sets.Nuke)
end
That's what I use and I haven't had any issues with it.
If you aren't too familiar with messing with luas, be sure to change sets.Nuke to whatever the set name of your elemental magic set is. You may also choose to set_combine your burst set as a part of your elemental set if you don't feel comfortable making a more complex argument for the Obi swap.