Corvette evolution within the Somtaaw fleet is an interesting study. For a time the only corvette in somtaaw inventory was the spare Ambassador craft stored in the mothership during the exodus. It was donated to Somtaaw from an anonymous source (which popular theory suggests was Karan S'jet herself), and served on Faal-Corum as the launch for ambassadorial duties.
As Somtaaw was afraid to dismantle the craft, studies on the blueprints available yielded knowledge to construct a lighter corvette using the modified Vaygr engine. While it produced a satisfactory light corvette and raiding vessel, Somtaaw knew it would need a heavy corvette in the near future.
The Somtaaw 'Heavy Corvette' was a study into such a platform that other variants could be based. The design was purely theoretical until the sixteen day war, where the defection of a Naabali fighter ace to Somtaaw yielded data on the Taiidan heavy corvette chassis. Lessons learned in the study refined the design, and solidified the plans for the Somtaaw heavy corvette.
It is not clear whether the heavy corvette was put into actual production or not. The original heavy corvette, after all, was retired shortly after the homeworld war in favor of the multi-gun corvette. As the light corvette already filled the role of shuttle and courier craft, the heavy corvette seemed to have lost all utility in its base form.