Get a fur rake and use that under fur, that is some awesome dubbing. There are some old patterns that will specify fur from different sections of the hide. Such as belly fur because it is lighter then the back fur. You can also mix it with other materials to give yourself some custom blends.
Narcodog, didn't realize that there were differences in groundhog hair based on what part of the body it came from (belly, back, etc) but will have to pay attention to that! I should have known that though cause calf tail is coarse and calf belly is fine, etc. etc. And I'll start putting that underfur in a zip lock bag for dubbing and dubbing mixes. I could call my dubbing mix GroundNarcodog or just Grounddog for short!