Shaping & Perch Training

[Stellae]

Sprocket, who is now 24 weeks old, is learning all kinds of things. I love the clicker, we're having a blast, and he is so eager to please.

About two weeks ago, we started doing some perch training, to help with left-pivots and because I'd like to do agility with him when he's older. I tried to shape the behaviour, rather than lure him up. He gets all excited now when I bring out the perch (he chews on it if I leave it out), but I'm struggling with two things, which probably is actually just a struggle with shaping.

He hops up on the perch, and faces me - but his back end isn't quite straight, it tends to drift to the left somewhat. He'll follow me around the perch, keeping his front facing me - but his backend lags (mostly to my left, but it is somewhat dependent on the direction I circle). How do I teach a straight-on "front" ? If I'm not moving, he doesn't either, and if I stop long enough, he hops off and sits down, and barks at me. So I guess I don't know how to shape it. I tried nudging him with a foot, but my balance isn't great and I move too much. I used a piece of wooden dowel rod to ever-so-slightly tap the side of his rear haunches, and that sort of works but he tends to overcorrect, and/or stop and sit (and bark). Sitting and barking at me is basically always the result of my attempting to shape a behaviour (on or off the perch).

I would also like to teach him to stay in the 'heel' position while we pivot around the perch. I'm struggling to teach this because he wants to follow me in a 'front'. We are slowly working on 'heel' separately, but he doesn't really like it, and I'm not seeing it's importance at the moment (he's doing better at loose leash walking, which is all I need for our regular walks).

So any tips for shaping, and specifically for shaping perch work, now that he's familiar with the perch? How do I help him not get frustrated (which is what the barking is, I think) and then disengaging?