Catalysis of the reaction: a fatty acyl- + an alpha-Kdo-(2->4)-alpha-Kdo-(2->6)-lipid IVA = an alpha-Kdo-(2->4)-alpha-Kdo-(2->6)-(acyl)-lipid IVA + holo-.
alpha-Kdo-(2->4)-alpha-(2->6)-lipid IVA lauroyltransferase