Hi orangetek,
had you time to figure out how many concurrent flows you actually need for your 600 subscribers? Does the maximum of 2^16? works noticeably better than 2^15? Basically, how low can you push this and still get good isolation? I seem to recall that the number of flows active in a core router is actually much smaller than one would naively expect... It would be especially great if you could report these results also on the cake mailing list, where Jonathan Morton cake's principal developer will see it and have a chance to chime in? See https://lists.bufferbloat.net/listinfo/cake for getting on the cake mailing list...
Best Regards