I'm finally calling my Rupnow Vertical finished so I thought I'd make a rare post (for me) in the Finished projects area. I abandoned the idea of mounting a fan for now and I still have to attach some rubber feet to the base but otherwise it's complete.
Here's some pictures of how it turned out, plus a video of it running pretty well now. At about the 1:45 mark I hand start it for the first time ever and it idles super slowly for me. As I suspected it is quite a well balanced engine and the vibration you can hear is mainly because of the 1/4" table top with virtually no supports flapping about. With some rubber feet and a sturdy table I think it'll happily sit in one place and run all day long.
Now for a big long wait til I can get back to my shed