I have the same problem. My daughter puts her feet on the back of the seat in front of her. Normally I would get upset, but she does it in our Aurora as well.
Until recently it was easy to just move the front seat a little further forward, or in the Z28 not worry because the fabric was scotchguarded. But now that she is 39 inches long/tall, the front seat of the GTO gets cramped if we move it up further.
I was thinking of talking to her, but usually her response is "yellow paci" or "pink baba". Somtimes I get a "dada car vrooom" or "dada car baaah".
Do I grin and bear it until she is say three and may listen, or do I take away her cheerios for a few days?
My wife suggested we put the plastic thing that hangs on the back of the seat in the GTO. such a dilemma, I hope GMAC doesn't hit me for too much when I turn it in at the end of the lease.