I've lived as close as Holly, MI for many years, so I have some knowledge of the area. I'd highly recommend getting at combo VHF/UHF antenna as well. One thing that you may not be aware of is WBKB (11.1, 11.2 and 11.3) from Alpena carries ABC and Fox programming as SD subchannels. CBS from that station is HD. Thus, you have a Fox alternative if WSMH is too weak to receive. WBKB is one of your stronger signals. Likewise, WJRT (12.1, 12.2 and 12.3) from Flint carries ABC in HD as well as a weather channel as a subchannel. Being in a rather flat area where you are located is helpful, but you are going to have to go for some pretty big hardware for successful reception.
However, if you want WBKB, you'll have to invest in a rotor, which I would install anyway. If you're on the roof, you might as well do it all at once.