You wanna talk about grossly undersized gestalts, look at Monstructor!
Check out this screen cap from the G1 cartoon where Dinoking is fighting Star Sabre and he's bigger than Star Sabre! Whereas the Dinoking toy would be barely up to Star Sabre's knee or thigh!

I don't think that Volcanicus is small it's just that Predaking is massive. But Monstructor and Dinoking are tiny even by G1 standards!