To date, I have not been very successful making big pieces. Anything taller than 27 inches must be sculpted in two pieces that will fire separately and then stack. The engineering is tricky...and I have to make it up as I go along.
I have big two pieces on my table right now and they challenge me to use everything I have learned. If I fail, the clay will be recycled and I will consider the time well spent because (as I have heard quoted) your failures teach you more than your successes. But there is a still small voice inside me that says "please let it work".