I've fully resolved the issue with the default custom allocator and now have complete runs with both the linear allocator and the default allocator. Issue was lack of deleter invocation in the non-detachable allocator scenario (which only affected use with the default allocator). Performance is similar, with the linear allocator slightly outperforming. Note that the power of the linear allocator is that incoming blocks may be fed across threads without causing a deallocation storm (major performance hit).
This was unrelated to the issue I was dealing with the other day, but I felt it was important to finally figure out what was wrong with the default allocator, since they appeared to be related issues. So everything looking excellent again, trivial fixes in both cases, and some other improvements along the way. Now back to optimizing confirmation.