In the Skybolt review, I used S9001's, but in my original Skybolt (Kit Version) I used S3003's and S3004's

The Skybolt does not need anything outrageous in the way of servos. It is not a 3-D plane, so it doesn't need the super-fast servo response that a 3-D plane does.

Standard servos will work fine, anything above that is gravy