Well a large floor entity will be treated by the engine much as a terrain is.
There are numerous issues involved here.
FPSC is designed to work on a tile based system - floors are supposed to be composed of tile sized segments to work perfectly. Such segments have particular parameters set in their scripts when made or otherwise edited so that the engine recongnises them as floors correctly - similarly other segments have a variety of special parameters set against them.
The engine sees an entity centre point axis as being needed to be lined up with the centre point axis of a model as created in a model editor - in FPSC case that means the Max definition of that.
Placing any very large model in FPSC you should pay attention to where its centre indicator in the engine is located. FPSC sees an entities position as be in the centre of the tile in which it is placed. Thats the tile which FPSC associates with it.
Obviously because of the tile based system large objects which extend a great distance outwards away from that centre location may cause some problems.
The contruction of the original model and how many ploys its composed of may have an influence - if the distance between polys are very large entities may fall through them as collision may be unstable. Just not enough polys. Try and make sure the polys are not larger than one tile that may help.
Or you can wait and see if any update improvements makes provison for such large entities to be included more easily.
At the moment its much a matter of trial and error until and if you can find a solution.
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