I've done this too but also have a DIY pin spanner that is slim enough to sneak in between the arm and the cup. I made mine from a length of cattle electric fence wire. Wire made to hold horses in the fenced enclosure. VERY tough stuff and hard to bend. But strong enough to hold and turn a well maintained cup during an adjustment. Not strong enough to free a rusted stuck cup. That takes crank arm removal and "the big guns".