[Mr. Pockets]

Just checked the math:
Not possible to dunk/drop balls into the hoops (Though you can get really close)

Barriers:
Fender: 38.75"

Now all the things to take out of that:
Hoop: Inside Diameter 18"
Backboard: 0.5"
Connection from hoop to backboard: 6" from inside of hoop to backboard
Total: 24.5" + some tiny distance for the diameter of the hoop ring (the metal itself not the gap in the middle)

38.75 - 24.5 = 14.25

You are allowed to extend out 14"

14.25" - 14" = 0.25"

So even under ideal circumstances your extention falls just short of the hoop. Dunking is physically impossible without tipping your robot somehow, or violating the rules.