yishbarr wrote:
General question: are props allowed to touch the inside of areaportals? (Touch, not stick out).

Props can; no problem; valve often uses areaportals inside doors. (so collisions with the model).
The only thing is that even when closed that specific model is rendered from both sides:

(image taken in aperture valentine, full bright)

As you can see; the brushes and models sticking through the areaportal (stairs and arms for example) are rendering on both sides; where the rest is just cut off. (Don't mind stuff on the sides it's skybox, couldn't find a better example )