I forgot to say thet the Carvair pallets were not standard wooden pallets but crude sheets of 1/2" thick plywood with steel rings round the perimeter.
When BEA started operating Argosy 100s & 200s the pallets were "stressed" all aluminium and the regular joke was that once the empty pallets and Cargo Documents had been loaded onto the aircraft there was no payload left for the cargo.
Shortly afterwards BOAC were operating Boeing 707 freighters with "Brownline" Pallets which were 125" x 108" and made from some type of composite material with aluminim edges, you could load 3500kgs onto each pallet, greater that the total payload of a DC3 freighter.
The Boeing 727 & 737 used the same "Brownline" pallets and KLM & Swissairs DC 9 freighters also had the same type of pallets but 108" x 108" to fit into the narrower fuselage.