My son (age 6) also took the RIAS a month ago. He got >160 on the total, 143 on verbal, and "177" (>160) on nonverbal. The tester said he got all the way to the end of the nonverbal part, which is normed for adults up to age 90 or so. He had also gotten a 99.1% on the Ravens test, which is like a nonverbal, spatial test.
For us, we are not pursuing further testing since these scores should qualify him for our G/T program.
Supposedly the RIAS gives higher scores than the WISC, etc. although the literature I have read said they are the same, not higher.
