My son has a similar profile to your son (with the VCI and PRI reversed).
We homeschooled K-4 and then my son entered a small private school the next year in 6th grade (skipping 5th). He skipped 7th and is currently in 8th. He is further accelerated in math (one year ahead of his current placement).
Because of his processing speed issues, he has accommodations at school where he is allowed double time on tests, but he rarely uses it.
Honestly, from a cognitive demand standpoint, two skips haven't been enough, but from an executive functioning perspective, it is bordering on too much. Since we don't want him to burn out before he even starts high school, we have decided to have him take a gap year (or two) before entering 9th grade. We'll be homeschooling again. I hope to work on skills that have been difficult for him and at the same time stretch him intellectually--something that's been lacking for the last two years.
