I'm in agreement with jlclark.  Also, if you are concerned about it getting wet before you get back with your second pass, that is a good reason to include some residuals with your first pass. It will buy some time.

The other thing that I noticed.... I never use more than 16 oz of 2,4-D LV4 pre-emergence on corn.... that would be 12 oz/acre LV6. Your 22 oz/acre LV6 sounds high to me. If you are concerned with injury to corn, maybe you need to re-evaluate that 22 oz/acre rate.

What are you trying to kill with 22 oz/acre of LV6?