You will DEFINITELY need hashlife. In fact, one of the indications of the complexity of this pattern is how slowly it runs even in hashlife. It's instructive to compare the speed at which gemini runs with the speed at which the demo patterns that come with Golly run. At maximum speed, Golly routinely cranks out so many generations that it requires exponential notation to display the number. Gemini by comparison runs very slowly even at maximum speed. This fact alone makes it interesting. It is not easy to design a pattern that Golly can't optimize the bejesus out of (try it).