I tried steeper than 2:1 and it was not a good idea for me but i suppose that depends on the type of clay, if yours is black and tan then I'd worry about the black being organic in nature as that is what it is here but might differ from what you are dealing with. The 2:1 slope even in a low wind area did erode and started to settle to the foot of the slope -making the slope even steeper...also if someone falls in its pretty darn hard to get out - not sure if you have ice there but it can make it dangerous. I found the 3:1 to be the best structurally, and the sunfish spawn on it in areas.

Have fun!