Thanks so much for responding. He's a big kid, so I doubt he'll really stick out that much. His best friend is actually almost two years older, so in general he's fine with older kids. But on the downside, he's definitely a kid who is slow to warm up to new situations/people and is pretty hard on himself if he's wrong.
I agree with you on the two years for Algebra. I'm wondering how much review there is - it might actually help give me some comfort that he won't have any gaps. I've found in general Saxon has tons of review which drives him crazy, but in this case may be actually helpful.
He definitely ready for more - if it was a single skip, I don't think I'd hesitate. I would just hate to finally have him challenged, and have it be too much of a leap and frustrating in the opposite way!