SQ7 FOH, DX168, SQ5 Livestream Mix

We currently have an SQ7 at FOH with all local inputs being utilized as well as a DX168 full of inputs as well. This is connected via SLink port. We are using all 48 inputs. We have purchased an SQ5 as well as an SLink card. We want to get all of those 48 inputs over to the SQ5. What would be the best possible way to set this up? I know that the SQ5 will use Trim instead of Preamp. Tie Lines have been suggested but looking for the absolute best way as I want each console to be almost identical as we sometimes have volunteers running them. Thank you.

Tie Lines is the way to go.
And setup to have SQ7 control Gain, then let both Consoles use Trim on the actual channels.

That way the SQ5 stream will not be affected by an unforseen change on the FoH console.