We used, regularly, to cart bullion around the country - Electra and B722. No different to other stuff (except for the artillery the police brought along for the trips).
(a) fuselage bending loads - the pallets were loaded centrally Really only feasible to main deck load due to handling considerations
(b) floor loading - no different to anything else
(c) doesn't have much of a vertical component - we could have played ping pong over the pallets
(d) no effect on handling as the mass is relatively concentrated near the aircraft CG