I decided to take another look at modest memory/CPU configuration as it pertains to the confirmability query. On my max machine confirmability takes a total of 2.5 hrs running concurrently with 1 hr download (with no checkpoints/milestone). However on a 32GiB machine it blows up due to paging, taking at least 1 second per block on average. This is a huge cost that I don't presently have any mitigation for. As it's a consequence of disk read, concurrency provides only a modest improvement.