Hey! Ok so I'm slowly trying to learn Firefly and I noticed that if you have 3 different mesh objects loaded with the same file, Fusion still treats them as 3 unique models so if you have a 5 mb house wavefront obj for example. It will use triple memory if you want to use the same house 3 times. So...after snooping around I tried something that seems to work.
Add an empty mesh object and create an event "Start of frame" for example and choose "Load static mesh" and when the dialog window opens, choose "Use expression" and then you right click the object you want to clone and choose "Get mesh path" then you do the same thing with the tetures. "Load material" and right click the one you're cloning and choose "Get a loaded material" and just use 0 for 0, 1 for 1 and so on. I have tried this with just a few objects so far so I don't know how reliable it is but as far as I know this doesn't increase the RAM usage. It seems to just check what's been loaded and then re-uses it. Maybe this is old news for most of you but hopefully someone will find it useful