I suggest you decide on either 3 under or split, and stick with that. Switching back and forth can't be helping your accuracy.
I remember the first hunting season after I switched from split to 3 under. I had shot 3 under long enough that I thought I was used to it. The first shot I had at a deer, I shot over its back. I looked down, and I was gripping the string split!* I think the reason I did that is that the last hunting shot from the previous season had been split, and even though I had been shooting 3 under for months, my mind reverted back to the last shot I had taken hunting, in the excitement of the shot.
* Edit For those of you who may be wondering if I went back in time, what I mean is that I had nocked an arrow for a possible second shot (which didn't happen), and glanced down and noticed that I was gripping the string split fingers, so I assume that is the way I gripped the string for the first shot, as well.