Should I set more $ aside in reserves for a duplex?

I'm possibly going to be buying a duplex as my first rental property, and had a new guy question. Show much extra should I be setting aside in reserves for a property like this? I was figuring if I was buying a SFR, I'd keep 15% aside for reserves (10% CapEx, 5% vacancies). I figure I should at least set aside another 5% (since there'd be 2 units), but should I set aside any more for CapEx too since I'll have 2 kitchens, etc? Thanks!