Change/modify outpost shell models (to fix lag)?

[Yago]

The framerate is mostly as smooth as a baby's butt. But when there's an outpost shell in the camera's FoV, I get a serious framerate drop. I could ignore/tolerate this if I didn't want an outpost building so badly. As far as I'm aware of how and why slowdowns occur in games, the outpost model probably has too many vertices. Don't take my word for it, though

Oh and, here are some specs: ATI Mobility Radeon HD 5400, with a 3GB RAM on Win7 and an Intel i3 processor. A laptop. I know it's not too fancy, but I think this should be able to run a game like Kenshi without framerate drops.