Need a combiner group. Most destroyer divisions are too small with four shipgirls. Unless of course you take say a torpedo squadron and have the light cruiser as the center part with four destroyers attached. (most of the pre-Victory combiners groups).
Or go six equals of either a Constructicon (Devistator) or something like the Breastforce combiners with six members (Liokaiser). Or the Seacons (Piranacon) with a large center unit and four that attach plus one that turns into a weapon.