I would not worry about pre-amp overload since the more powerful Canadian channels come in, the transmitters for the missing channels currently are VERY low power and directional, not in your favour, Hamilton is also a weak transmitter.

The best option is wait it out until next year when the Canadian go fully digitial, higher power and back to their assigned frequencies.

How are analogue Chn 57 CITY TV, or the Omni ones coming in? A few of these on on Commerce Court or First Canadian Place and not the CN Tower.