Right now I have to say I'm feeling pretty good about our choice to have only one child

LOL! I'm with you, too, acs. We have two boys, of course, but we had an HG+ one first, and we had the second 3 years (almost to the day) later, so even if he's HG+, too, he's not likely to overtake his big brother.
It seems we planned extremely well, too!

Good for us!
:p LOL!
Oh, and my sister and I are only 17 months apart--one year in school. I was the shining star, but in any other family, DSis would definitely have been the bright light. It was hard on her to follow me, and we still have trouble getting along (she has a bad case of RE, and we know how well that works with my personality...NOT!). This was without any grade skipping, too.
Actually, now that I think of it, grade skipping her into my grade would probably have been helpful in our case! It wouldn't have bothered me in the least, but it would have been really good for her self-esteem.