Paddy,
Sounds like a job for a hewing adze. I’ve seen ‘em in all sorts of sizes and
profiles in antique shops over here in Ohio Amish country. Flat, round and U
shaped. Even short, one handed ones. I helped hollow beams to hang from a
ceiling in a new construction big, expensive house. We hollowed them to reduce
the weight. A lot of heavy but never the less rewarding work.
As an aside, I just went through the same sewer disaster but it was a neighbors
tree so unfortunately I can’t chop it into bits. As much as I would like to.
-JP