If you are spraying at 7 gallons per thousand and you are adding 200 pounds of urea to 300 gallons that means you are applying over two pounds of n per 1000 square feet. That is way to high of a rate on any type of grass. Why would you spray at 7 gallons per 100? If that is your true rate then you are only able to get 42,000 per tank. By the way if you read the lable on Mecamine D you will see that it is the same rate as three way or most any 24d product which in my area is 1.5os per 1000 sq ft. and you should be adding half a gallon per tank if what you say about your application rate is true.
Try me first, try me last, just try me.