2o2o vs 4 on?

Razzle is 44 lbs – he ought to be able to handle a solid 2o2o on the teeter, right?? But I have been wondering about this since his back legs have been drifting up with the (real) teeters in classes so often in 2020 position… (our home board isn't weighted right) So, we did a little work on getting him to shift his weight back in position on the teeter but I seem to either pull him off when tugging (I guess since the teeter lifts his hind end up in the air sometimes SOOO he doesn’t see this as a rock solid HOLD position now) or I toss a ball badly that he leaves position some to get it…

***so I guess my question is how do I now get a rock solid 2o2o? I am guess I move it back off to other objects like rocks and tree stumps and stairs… but how do I tell him he is not allowed to move his feet at all????
or is it better for Razz to switch to a 4 on???—-will that be too confusing now and also, I have no clue how to train that… because even though he doesn't have a perfect 2o2o its a "retrain"....