Climb020
ArboristSite Operative
Really need more information to decide to climb it or not. Is there another tree close to tie in to? Is there a lean? If so, where is the rot in respect to it? With 60% rot it more depends on exactly where the rotten/hollow spots are. With something like that and no rome for a bucket, I would probally try to remove as much weight as possible before going up. Could use either a power pruner and a step ladder, that is within reason, or a rope chain to get some of the stuff higher up.