I am currently making a ratan grip and I have a couple questions.

First, I am using cork for the under-grip. Is this acceptable, or should I use a light weight wood?

Second, I understand that you wrap thread between the turns of the ratan after the under-grip has been wrapped. Is red thread the standard color used, or does it usually match the thread used for the wraps? Also, what size of thread do you use on the grip?