First thing you do is the Math. How many gallons do you want to apply per thousand sq ft is the first question you must answer. Next is your Ground speed and then your boom width to find the size pump you need.
Important point is Pump rating. That 2.1 GPM pump is rated at Open Flow or zero PSI. As the PSI increases the GPM decreases.
Good luck you need it.
it is one thing to do a off label applications. It is total stupidity to post it on the world wide web and expect people to approve.
You can lead a Donkey to water but you can't make the Jackass Drink