Fitball Exercise

chipembele

Hi
Does anyone use a fitball for exercise?

My PT started me off on a few but its the chest press that i'm particularly asking about here.

I'm 5ft 6 and bought a 65cm one but I felt it was too big so I bought a 55cm one but that now feels like I could be doing myself damage when doing the chest press.

It seems that either my neck isnt supported or my back isn't supported. I'm told using the fitball is better than bench because it helps with core but if its doing damage I may be better off just buying a bench.

What do other people use?