Thanks wimvdb :-)

It sounds like what you're finding is the same as I'm getting, more or less.

I've been doing some further experiments too and it appears to me to be a camera range issue in Poser that is actually lying behind this. There seems to be an absolute limit, above which the camera stops seeing... or perhaps, a limit on the z-axis above and beyond which Firefly stops rendering?

So, maybe its a Firefly issue. If the latter it may be influenced by system resources I guess.

Anyway here's my deductive process...

I scaled my model to 100% then composed it at as side on an angle as possible to the camera.

Set the camera Yon to 860000 (the maximum dial-able Yon). I then started to increase the ZDoly value for my camera (the Aux camera in my test).

I found I could make the model start to disappear when the camera's ZDolly parameter was dialled above about 7000 to 8000 (relative to the model's  or so... meant to note the exact value... drat! This is why I'm not working at CERN. Or part of why... ;-)

Anyway this happens regardless of what zposition I dial my actual model too.

I fiddled around adjusting the fstop for a bit... don't really understand what THAT is if I'm honest.

But then EUREKA! I have just figured out the answer.

Camera scaling!

Keeping the camera's ZDolly within the apparent limit (I set it to a safer 5000), upping the Yon to the max (for good measure) and then simply scaling the camera to 120% (so that the whole model fitted into my render frame) and hey presto the whole model has rendered at 100% scale.

Ta da:

This all means basically that I can stick some runtime character or other in a spacesuit, in or on or about the hull, in closeup frame, perhaps have them holding a graviton wrench and tinkering with a bit of nurnie detail (once I add some more of this to the model)... but have the whole ship receding away into the distance... in order to give a hopefully monumental sense of scale!

Obviously I will have some more experimentation to do now with how the perspective dial etc affects / relates to camera scaling, I guess... in terms of getting the above to work... once I actually get the model finished! I have a feeling UV mapping this thing is gonna be the death of me...

But I think at least my initial problem... of the mystery of the dissappearing model, might be solved.

Many thanks for all the helpful replies so far :-)

Can anyone out there shed any more light on this whole thing though?