I modded my CM4228HD as per Ken Nist's excellent article. I removed the hex screws holding the rods with the plastic balun box. I added a separate balun to each of the two antenna sections and a combiner. Measured with a laptop at the antenna using WinTV's Digital Signal Quality Meter I saw an increase in SNR from 27 to 30. I receive 4 digital stations, all broadcast from Camp Fortune at about 30Km north. The analog VHF Hi stations are also very clear; the VHF lo are a bit fuzzy. I'm about 5Km from Herbert's Corners, the other local broadcast tower; it's to the south. The UHF analogue stations and Ch 11 are watchable, but a little fuzzy. They are being received from the back of the antenna! The whole rig is in the garage rafters on the north side of the house.
I then took a CM4221HD and removed the bowtie assembly. I mounted that to the back of the CM4228HD; I'll call it a CM4229HD. I added another combiner that merges this new antenna section with the output of the first combiner of the modded CM4228HD. I saw no loss in the SNR meter and the picture quality of the VHF-Hi & UHF analog stations in the north direction were all still excellent. But now the UHF and Ch11 from the southerly Herbert's Corners are also very good. There is a slight multi-path ghosting on some of them, but still watchable.
Next, I disconnected the laptop from the antenna and replaced it with the 20 metre cable that leads to the VHF/UHF input of an Eagle Aspen S-4180-GX+ multiswitch. It mixes the VHF/UHF signal with the input from the satellite LNAs and distributes it to TVs and radios around the house. The loss for VHF/UHF through the multi-switch is 5dB. The signal at the TV outlets was pretty degraded. I couldn't get 2 of the digital stations from the north; most of the analog stations were very fuzzy.
Next, I put a CM7777 preamp at the antenna. This seemed to overwhelm the input of the tuner. I added a cheapo splitter between the preamp power supply and the multiswitch as a 4dB attenuator. That seemed to clear things up pretty well.
So, I'll probably leave everything this way until Canada's digital switchover and decide if it's worth the effort of putting this rig outside.