This hack allows you to twiddle the max number of units and structures you can create. Go into your drive letter:\jpog\data\unit directory. Open the following files using a text editor (like Notepad) and search for the line UnitSpecific for each one. Change the value to something you like, then save the file with a .ini extension:

HerbFDsp.ini (herbivore feeders)
CarnFDsp.ini (carnivore feeders)
Toilet.ini (bathrooms)
Hatchery.ini (hatcheries)
HuntPlat.ini (hunting platforms)
Kiosk.ini (kiosks)
shop.ini (shops)
hvdome.ini (viewing domes)
hventry.ini (viewing vents)
safari.ini (safari rides)
Road.ini (roads/paths)
rangerdp.ini (ranger stations)
ViewPlat.ini (viewing platforms)
turret.ini (security turret)