A very interesting design. I'd be worried about the latches holding the pack failing in flight though.
This got me to thinking; with the prevalence of standardized container shipping nowadays I'm surprised there hasn't been a cargo plane designed specifically to carry them, seeing as how entire ships and trains are designed for them. A plane with inter-modal containers could offload directly onto waiting trucks and speed delivery of their goods.
August 10, 2012
Converted from C-119B 48-330 c/n 10312 to become the sole XC-120 Pack Plane. Most of the lower fuselage removed and additional forward undercarriage added to replace the nosewheel. The pack is being rolled into position. From Fairchild 60 years ago.