On the Adox bottle it says:

If diluted between 1+20 to 1+50 the toner changes the image tone to a reddish brown.
If diluted 1+100 to 1+400 only the DMAX will be optimized and the image stabilized.
• for toning 1+20 bis 1+50
• only for image stabilisation 1+100 bis 1+400

Considering what many have written about the behavior of Ilford MGIV RC with Selenium (that it won't take on a color change so easily... which is fine, I don't want a full-on drastic color change!), I'm thinking my starting dilution should be 1+100.