Since you have a CM-4228HD you'll be interested in this page
comparing it with the older CM-4228. Spoiler alert: the author really
hates the new design. I doubt that it's as bad as he claims, but he does offer suggestions to improve it.
I'm using an old CM-4221 (4-bay) for UHF and a twin-lead folded dipole cut for ch. 6 for VHF (6, 7, 12 and 13) in my attic looking through the roof (slate and wood). That works very well for my stations, all in the same direction about 10 miles away. For my sister in NW Tucson, 9-12 miles from the repeaters, I used the ch.4 antenna for VHF and a Zenith Silver Sensor for UHF outside under the eaves of her back patio roof so they don't get rained on (I'm told it happens occasionally). That usually works but some stations are marginal. She didn't want an antenna on the roof.
While experimenting with the Silver Sensor I was sometimes able to get a watchable picture from some of the Bigelow transmitters, suggesting that a better antenna might work for them. Worth a try.
Depending on the vintage of your HDHomeRun tuners you might find that they don't receive all the stations that a TV's digital tuner will. I have two 2nd-gen Duals and a 4th-gen Dual, and the newer one is definitely better on weak signals. If that's a problem for you, a low noise
preamp might help but preamps introduce their own set of problems and I don't recommend them until you've done everything else you can. Cheap preamps and any distribution amps, especially cable DAs, are not low noise.