He was having such an easy time with this that I ended up moving right into Saxon Algebra . The incremental approach is the same, but there is enough new material that he is challenged by it. I don't know what will happen when he moves into Algebra proper. I've heard Saxon isn't as good in the upper levels. But if your son seems ready, I'd start him in Algebra and see how he does.
Some kids can zoom through their math lesson while others take the full hour.
You will almost always need to do logic with the child. That has been my experience, anyway. Of course, it all hinges on what kind of materials you use. Try and find self-teaching materials if possible. The year we used Bob Jones Geometry and a different chemistry course was a hard year for me.