Get down to 400 and add 50grains in the point, you should be at the right dynamic spine
The 500 spine @ 31" is too weak with an aluminum insert and 100g field tip. The 400 spine @ 30.5" is still a little stiff with a 100g brass insert and a 300g field point. That's already heavier than I want to go. The 400's may shoot at full length, I just haven't bought a full length 400 to try yet.
Not sure about everyone else's experience but, in my experience changes in point weight with carbon arrows don't make as big of a difference as it does with aluminum but, small changes in length make a big difference with carbon.