Thinking about mid-caps (DON) in particular, and what they might offer me

SCHD holds a significant percentage of my portfolio. I’m a retiree and I like the fact that SCHD is steady and boring. I like steady and boring a lot. I’ve been thinking about opening a position of DON, also nicely steady and boring, to add some diversification through mid-caps, but the finances are throwing me off. I look at SCHD with a much lower expense ratio and a higher yield, and I see DON, between expense ratio and yield, with a significant drag. That drag is money I won’t get that I coul