I've never used the bow bolt system so I'm not speaking from experience but I would definitely add phenolic if it were me building the bow. You could probably get away with it in a lighter lb bow but why take the chance of ruining a good bow. I would say most not all but most bowyers who build a 2 piece take down are re-enforcing their risers with phenolic or a composite of some type.
Move this over to the bench maybe some guys over there have more experience with the bow bolt.
Cory