I was looking at that prison pack and it is tempting. Yours is looking good, but putting together all those pieces just seems very inefficient vertex/polygon-wise. I remember when I was building my pueblos, I made them out of segments. A hundred or so didn't make much difference in frame rate, but at some point, the frame rate plummeted, and it was within a difference of just a few more "segments". Building something as large as your prison without optimizing those meshes is probably dragging it down even further than Reloaded's already low rate! Looking good, though! I wonder if those pieces will be usable in the conkit, as that is supposed to be able to optimize the final mesh, getting rid of those unnecessary polys.
MAME Cab PC: i7 4770@3.4Ghz (passmark 9945), 12GB RAM, Win 8.1/64, GeForce GTX645 (passmark 1898); Shiny new laptop: i7 4800MQ@2.7Ghz (passmark 8586), 16GB RAM, Win 8.1/64, GeForce GTX870M (passmark 3598); Old laptop: i5@2.3Ghz, 8GB RAM, Win 7/64, Intel 3000 graphics