@xplosys, Im happy to hear this. nice one.
Yeah, I agree.
With your windows/openings facing visible segments and getting low fps could have alot to do with the level within the segment area you are looking at, thats if its in game that way. such as entitys, triggerzones etc that are behind the wall in the distance.
Apart from maybe reducing entity count in both areas, this doesn't really work for the game levels.
Try adding a opening on a wall in a small area like hallway or something with limited area behind you, where ever you like that works, and build a segment block (no contents) or segment wall like your buildings or other, at what ever distance works for the visible area outside of the map level. Depending on content that may be on the remaining level behind these areas or in front of it, it may or may not work.
You could also try adding floor to join your level wall to the outer fake wall, though I believe without would be better. Thats if you try it.
Also I cant remember what weapon was in the demo.
Weapons may be one of the cause's also, Im not sure if it depends on the detail of entitys visible to the player or being outdoors holding a weapon, yet I only found it so far with a ww2 weapon. As much as ive been working on lag, I never noticed weapons before. the drop was -10. I have some shots that i may post in one of my threads. Not real exciting though,
Anyway, the piranhas look great, my grandmother has a stuffed one at her house on a stand. yours look like it. Nice work.

"in videogames you try to get the best graphics with the least amount of processing." -Ingolme