I don't think a single-piston four stroke runs any smoother than a single-piston two stroke. Why would it? Multi-cylinders are a different story.

I'm a gas or glow advocate usually, but the G-26 needs a bit of vibration so the diaphram pump will work. I believe it has even been recommended NOT to put a dampening motor mount on for that reason. (I can't remember where I read that - Bennett Built's website, perhaps but that might have had to do with a smoke pump installation). For a video platform I might be tempted to go with an electric motor, though I have avoided that route so far.

The alternative would be to go gas and put dampers on the camera mount. Now THAT sounds like the ideal solution.