While there is a great deal of clear feathering, i would be inclined to say that this bird is a SF dominant pied. There is still too much colour and striping present for me to be convinced that it is DF but i would be interested to see what others think.
He does have more markings than most double factor dominant pieds but he also has a lot less markings than most single factor dominant pieds. I think that the only way to be sure would be to breed him with a normal hen and see if all the chicks are sf dominant pieds.
There is always the possibility that he is a combination of dominant pied and clearflight pied, this combination usually has more clear areas than either of the parent mutations and they are sometimes mistaken for double factor dominant pieds