I was going to give you the same warning.  I sprayed 12 oz of Cobra many years ago before RR beans and I found that I didn't need the foam marker on except for right where I turned around because by the time I got back to the other end of the field, I could tell where I sprayed because of the leaves cupping.  It really didn't seem to hurt the yield though, because that field was right up there with the other beans on that farm that didn't get the Cobra.

Mike