With you coming back with 1.33 pint of S-metolachlor, I am concerned that you are going over labeled rates of total metolachlor for the year.   Realize Stalwart has Metolachlor, not S-Metolachlor.   My understanding is 1.33 pint S-Metolachlor = 2 pint Metolachlor.  That is the conversion rates that I use.

Go back and recalculate how much total S-Metolachlor/ Metolachlor you are applying for the year with your planned program.  The label mentioned illegal residues if you over-apply. However, I will say that I have seen metolachlor damage to corn. So, to me, this is not a theoretical discussion.  Yes, I think you can damage corn. That is my assessment. 

When your dealer is recommending a 2.5 qt/acre rate, I wonder if he is aware that you are coming back with more Metolachlor in a second pass.