It's completely possible that the Shivans seen in the FreeSpace and Silent Threat cutscene/video aren't the only type of Shivan that there is. There could be various classes of the little things; one for piloting fighters, a worker type class, a close-combat soldier, etc. I have absolutely
no evidence to support this theory

, but there isn't anything against it yet. Still, it could be an explanation as to how they squeeze the buggers into tiny fighters like the Dragon. I guess they could just be really good at squeezing into tiny spaces as well.
As for asking a Terran Alliance pilot questions:
"Do you ever get disturbed shooting down other humans in the NTF-GTVA civil war?"
and....
"I've heard Admiral Petrarch and various squadron CO's aboard the Aquitaine say some pretty outstounding stuff about this 'Alpha 1' character. Do you ever get jealous of this guys' extraordinary success?"