I started with Sitka Spruce two years ago. I never looked back. They are about 10% lighter then POC and much stronger indeed.
My last batches from Hildebrand were as follows:
Full lenght, 53 lbs: 10,1 GPI as average
Full lenght 59 lbs: 10,6 GPI as average
Most of the time they don't break when hitting trees. However, they can get hardly visible fractures. This means that the shaft is almost completely broken, but you can hardly see it. However such a shaft is mostly bent too and when you want to straighten it it will crack or bent in all directions like it is rubber. A close inspection will show you the fracture.
It is my experience that the raw shafts aren't very straight. But they are easy to straighten with the screw-driver method.
Alltogether I can recommend them.I you want a light shaft yet very durable, buy them!