Externals are still the way to go if you are dealing with very heavy loads or odd shaped, unwieldy loads (90 pound Columbian Mammoth mandible, anyone?). .......
The next time you need to carry a Mamoth mandible you should consider an Alaska Freighter Frame
. They are much favored by Alaskan big game guides for hauling out meat, moose racks, and other brutally heavy and/or awkward loads. I believe they are only available from Barney's, a local outfit here in Anchorage. Barney's builds them to be totally indestructable. I have one that has served me well in the past. In my old age I don't do so much of that kind of heavy weight packing anymore so it doesn't get used very often these days.
I have no connection to Barney's, but I can recommend their gear.