That UPS is twist lock for a reason - I believe the lowest draw a 110 twist lock will have is 20 amps. IIRC, APC's biggest 5-15P plug UPS used to be a 1000 or 1200.

Plug model MP-121CR is an assembly-type plug, and model MP-121CR1 is for molding onto cable assemblies. Jack model MJ-179LR mates with both plug models. Pricing for MJ-179LR jacks is $0.32 each ...