I did alot of reading and testing and MY F75 gets great depth and I am convinced that on mine the DST 9.0 is off. It gets the best depth in ground and out of ground. It's chatty in 9.0 but a good target still comes through fine. In 9.1 I loose about 2 inches or more but extremely quite even at 99 sensitivity in the house in any mode. No matter what all I've read My F75 has all the symptoms of being 9.0 being off and 9.1 on.
Ronk
Ronk