Helix fi channel

The above solution is sound, however I would like to add a few details: 

It's much more convenient to do this using Helix-Fi ( https://helixfi.videotron.com or using the Helix-Fi mobile app ). You can do this from the Connection tab, then going to View Network and Modify. You also don't need to be connected to your network to do this via Helix-Fi (you can do this from Mars as long as you have an Internet connection).

The Channel selection options will only be available on Helix-Fi after the SSIDs have been split between the two bands. 

If you are using Helix Pods, it is not possible to separate the networks by band, therefore this solution will not be available. However, the Helix Gateway (like most routers) will typically pick the least congested channel when it reboots.

Happy Holidays!