My 4 yr old was sent away to be professionally broken at 3,he was ridden in a hanging cheek snaffle,which is what I bought him when he came home,hes been going well in it up to recently and I'm wondering if the poll action is too strong for him as he throws his head sometimes and was especially difficult to ride 2 days ago.He has had his back checked and his teeth are being done today,so this may iron out the problem.I am thinking of changing him to a happy mouth snaffle instead,he is a big strong horse but equally is young and green any recommendations?

I really like the Sprenger or Neue Schule bits. Ergonomically designed to be comfortable in the horse's mouth and made of metals which warm up quickly and encourage saliva. Many have a lozenge in the middle.
If so, it is essential that the bit is not too big as the lozenge will not remain in the middle of the horse's mouth if the bit is sliding from side to side.
Ask your vet or equine dentist about the conformation of your horse's mouth as this will help you select the right type and thickness of bit. Things like a big tongue, a low roof to the mouth etc will effect the sensitivity to the bit.
Obviously check for wolf teeth too! Good luck
ps. you can hire bits to try them first. See www.horsebithire.com