The Tarot Stirling engine is a scaled down version of Jerry Howell's design.
That the Tarot runs so well is a testament to it's manufacturer. It is among the best quality pieces at nearly any price.
I have seen examples built by machinists to Jerry's plans that were never able to run. Building these requires precision and skill.
I have also found the Tarot does not need a cooling fan as it's fins shed a lot of heat on their own.
Gil