instead of a the 'a4af' sources being balanced across all the files,
stacking them all on the most complete file makes more sense, then after that file is complete the 'a4af's' stack onto the next most completed file (..or the next file with least sources...)
reason is, when they're balanced, all the files with a4af are disadvantaged at the same time, why not give one file all the sources they is, then work backwards, so each file gets the best chance.