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Join Date: Sep 2009
Location: Minneapolis: DL DM charter 2.3MM
Programs: A3*Gold, SPG Plat, HyattDiamond, MarriottPP, LHW exAccess, ICI, Raffles Amb, NW PE MM, TWA Gold MM
Posts: 102,619
I'd personally be nervous about changing the credit card because if there's a problem later, such as Hertz claiming that the car was damaged, both credit cards could refuse to protect you.
It would also be a mess to fix if Hertz somehow charges both credit cards.