Whether is dips 40º or so depends on a combination of factors concerning the NDB station itself. G1000 doesn't intrinsically have a high degree of sensitivity, but instead it's the ADF antenna. From personal experience... the C172SP's with G1000 have a very decent antenna on the bottom of the cabin and the G1000 dip is not 'that' much as in a conventional ADF equipped aircraft. (It also makes a difference whether you are tuning the NDB with a independent ADF receiver, or with the inbuilt G1000 one, on the same G1000 equipped aircraft).