I think that belly should be bigger?

No. Belly should be bigger when he is standing. He just lies here.

Alexbguy ist right though, it should be bigger.
If the lady was in the horse belly, it would not only sag down but also bulge on the sides. Try looking up pregnant mares, I'd say you can roughly compare the mass of a foal with that of a grown adult human.

In case a horse with a belly of that size laid on it's side like portrayed in your image, the mass would not magically vanish. Shift a little due to the different position, but it would be still a visibly massive gut. If there wasn't the vore tag and the title on this picture, I would not have thought of it as vore, as the lack of a properly sized belly does not make it look like the lady is inside the horse.



Though maybe she's digested already?

If you want bigger bulges, then you will get them :D I have 2 or 3 horse vore series already rendered and there is bigger bulge, so don't worry :D

heh, good horsie~