Are custom 3d monuments possible?

[trist1322]

I've been playing around with creating custom monuments visible on the map, getting a feel for it by essentially finding all the files related and copying the Big Ben but with new name, all files named correctly and custom icon, but despire having what seems like all the right files, the big ben model doesnt appear on the map. is there something hardcoded that would prevent modders from place custom 3d models, or am i missing something?