To be honest this is probably the biggest drawback of IMOX/raptor. I use it sparingly in my rotations because I am afraid of some of the residuals causing a failed plot. I will say that last year I used IMOX around the middle of May in my clover. Then I learned I wasn't suppose to plant brassicas for basically one year. I went ahead and planted in the middle of July and I did not notice any issue with germination. Tonnage was great also.
I did find a study out of Oregon State saying they did the say thing, and they noticed no difference in tonnage when tested against a control. Does anyone know what the Thunder interval is?