I agree - mostly because of leaks in the aux (bladder) cells. There was a period of time where it seemed like we had a aux cell leak on almost every aircraft. Standard fuel load at the time was 36K for a trash hauler, and config was either 8-7-3, or 7-6-5 (outboard to inboard) keeping as much fuel in the outer wings as possible, for as long as possible (to lessen wing stress). The externals were not used unless necessary for a higher fuel load. If you had one aux cell out, you would try to squeeze 8.5 in the outbd's, 7.5 in the inbd's, and 5 in one aux (and hope the aircraft wouldn't start venting before take-off). 40K was standard on HC/MC's, but you had the Benson tanks so no worries even if both aux cells were leaking.