Tail amputation at an older age is a painful recovery for a dog.
They have phantom sensations and pains just as any other amputee does because of the nerve pathways that have developed through the use of the tail.
Docking of baby puppies may cause some amount of pain and discomfort, but they are quiet a soon as they are put back in their basket.
I have observed NUMEROUS dockings, and I find it NOT to be cruel. The puppies do not freak out. They just go back to sleep when they are put back in their basket.
I now tie tails, which is less traumatic for the bitch, and makes a very nice dock.
Tails get tied on the second day if puppies are vigorous, and right before a feeding.
They do not cry or whine, no one gets upset, and tails are usually gone within 72 hours.
To the OP, I would strongly suggest you reconsider docking at an older age. Your dog has lived his life with his tail. Dogs "talk" with their tails. He will really really miss it if you dock it now after he has grown used to having it and using it as a social tool and navigation tool.