First point - not enough information -
(a) what are the spreader physical characteristics ?
(b) what realistic effective area of the spreader can be used to distribute the load ?
(c) what are the aircraft floor characteristics and limitations ?
The problem is that we are trying to determine what the floor structure is seeing in terms of
(a) intensity of loading - kg/sqm
(b) running load - kg/m
I think we might want to see some more information ... ?