Hi Chris,
I haven't used ours to rake yet, but envisioned either using it in a mostly flat/horizontal position pushing forwards, or in a moderately to steeply angled position going backwards.
What angle did you use it at?
When we tried to move piles of rocks without the bar, it just stalled, (actually we got to the point of spinning the tires) without much ability to penetrate into them, but with it, we could pretty easily fill the bucket- although to be honest, we did kinda jiggle the tilt while pushing in (like you would with a hand shovel), and while that didn't seem to help much pre-PTB, it greatly helped with the PTB.
Good luck with it, and keep on tractoring- safely!
Thomas