Yes, instead of stacking, you connect them via the Pixhawk connectors like described in this post.. The board was intended to use ubox boads from the gnss store, which would fit into a very small IP66 housing, but unfortunately they’re much more expensive. So I think most people will use Ardusimple boards.
Data handling is done with Matthias/Franz’ software (great work!), but some pin definitions have to be changed (different type of board in order to fit into a small housing)