When is a tree not safe to climb.

[Jesse]

As all of above, but also be very careful that you don't over load the main scaffold or stem by dropping too much from the crown in one place in one go, work evenly around the canopy, one side then the other until you pull it all into a pole, if its Meripilus, or Ustulina make sure you double your day rate, and if possible fell it.

[Paul Cleaver]

it should be ok but for anchor points choose twice the thickness as normal