Using same Effects loop for 2 heads, RJM mini line mixer

Trying to accomplish 2 things:

1. (Simple) Best place to insert rackmount tuner.

2. (More Complex) How to use the same units in the effects loop in the effects loop of Both Mesa Heads without having 1 a slave.
Units I'm talking about. 1. T-Rex Replica & 2. Both Line 6 (Echo & Mod Pro)

I have a RJM Music Mini Line Mixer. I was told this may make it work, But not sure how to make this work....

IDEAS.....?

1. In front, after the first buffer.

2. The line mixer will let you mix the two FX sends, and then you will run that into your effects boxes. The last output from the loop effects should be split with a Y-cord or splitter box into the two FX returns on the amps. This will let you either switch between the two preamp sounds into the effects, or blend both. HOWEVER the signal to the two amps' power sections will be identical. You can't split the individual amp signals back out of the mono effects boxes.

3. CLEAN UP THAT SPAGHETTI FARM :shock: