Years ago, the late Elmer Trett had a billet lower end made for his TF bike. It didn't work. The billet material was so dense that it moved all around when it warmed up. The main bores would be out of round by the time he got back from the burnout.
He reline bored it everytime, and it continued to do the same thing.
Then Chief Auto Parts made a billet block for Eddie Hill. Elmer talked to Fuzzy and told him about his experience. They tested the block, and apparently had the same issue.
Would be interesting to know how they have worked around that in todays blocks.