Asking for more aid?

I don’t want to sound ungrateful for how generous Oberlin has already been, but has anyone successfully argued for a bit more aid based on other schools’ offers? There’s about an $8k difference in the overall costs between the best offer and theirs, plus increased transportation costs to get to/from Ohio. I know some schools basically say, ‘if you have another offer that’s better and it’s impacting your choice, talk to us’ - has anyone successfully and tactfully had any luck here?