>>how do you attach the feet/spikes/pods to the component<<
When I have to attach a cone to the underside of equipment where the cone has a flat top or there is no option for a bolt, I use appropriate size GrungeBuster dots from Herbie's Audio Lab. These can be ordered with adhesive on one side or both sides. The Grungebuster dots (also available in sheets to cut to needs, or for interior damping) are made from a flexible elastomer that attenuates mechanical energy and despite its flexibiltily, compresses very little. The adhesive Herbie's uses is tenacious but removeable. This is sonically and mechanically much better than Blu-tak. GrungeBuster Dots are here: http://herbiesaudiolab.net/gb.htm.
>>unquestionably the best tube I've used in this DAC. So much detail and separation compared to any other tube, even the Bendix 2C51.<<
Bendix 6385 is a spacious and revealing tube in this circuit. I think preference for it is going to be quite system and listener dependent however. Of the many tubes I've tried, the Bendix '60s 6385 is the most detailed, spacious and articulate, but the Bendix 2c51 is close in these respects and its tone density counters the leaner sound of the 6385. I find, for example that the 6385 vs. 2c51 is a close call in the Havana Balanced in which I am using PCM56P-K chips, with one tube being preferable on some music but losing out to the other on some performances. We're on the fringe when we're changing output buffer tubes in our DACs by the album or track! But the 6385 is definitely not the right tube to use with the AD1865 chips in the Havana Balanced. The AD1865 bring exactly what the Bendix 6385 does, but at the point of D>A origin: more definition, more articulate leading-edge transient detail, more event separation but leaner tonality. With the AD1865 chipset that I run in my second Havana Balanced, the Bendix 2c51 sounds tonally and harmonically more complete. I am interested in trying the 6386 to see if it splits the difference. I just got Russian 6N3P-DR to try as well. My Bendix 6385s are from 1964. The '64 is reputed to be the grail version. I haven't heard the 1966 production. I wonder whether you'll prefer it to the '64 when you get the latter.