I've done this in a canoe with a Verascope on a lake. Used the double exposure shutter cock, covered one lens with my palm then drifted a little and exposed the other lens. Used pine trees in the distance to overlap the frame. It came out really cool like a scale model. the lake was really flat so that worked ok. I also did this at Mt St Helens. Having a subject you can easily frame the same scene simplifies things. Good luck. It creates a neat effect.
greg