Read through as many resources as you can find, including, as Val points out, both positive and negative comments/research on acceleration (though most of the research is positive). But ultimately:

1. Every individual is different. It's great that a particular solution worked for someone's child. That's not your child.
2. There is no perfect solution for HG+ students; they are all compromises, it's just a question of how you prioritize the compromise.
3. You and your child will make the best decision at each point in time, based on your knowledge of your child, your family values, and the resources available and appropriate to your family.
4. No matter what you do, someone will judge you for your decision. Listen politely, of course, but remember that they don't know your child like you do. Don't bother to engage 99% of them; it's not worth it.
...pronounced like the long vowel and first letter of the alphabet...