My dog is working through transition, and I have noticed, particularly at longer distances (60 + yds) his whistle sit is getting worse from square. He will sit immediately, sometimes adjusting himself to near square, but sometimes not so much. Generally sits facing the right, and turns to the right to stop most of the time, when on a line. Any tips on how to reinforce square sitting??? I can hit him with a come in whistle and he will square right up, but I dont want him to get reliant on that. Any help would be much appreciated......