Well, You can put 2 models max per upload. Put one in normal and other one in portrait.
Other is impossible as far as I know.
Just upload em all each, and then put em in a pack.
Why you want em in 1 folder anyway? If its to get more downloads, it doesn't matter. If its because they are similar, still doesn't matter. There are many sets uploaded separately, and then put in a pack (pack can be made only of uploaded approved models).