Frank & GThrush your solution is already available. May Audio Marketing sells nice boxed sets of BBC cones/spikes (whatever you want to call them) that have adjustable threads with integral knurled jam-nuts. They are gold plated brass & are available in different sizes, from fairly small to quite large, & they do not cost a fortune. After you adjust the spike thread downward until the spike firmly contacts the floor, you spin the thin knurled jam-nut tightly agaist the upper mount section of the BBC cone. It makes a very stable mount. The knurled edge of the jam-nut is very accessible & easy to tighten with only finger pressure. These boxed sets also come with gold plated brass pucks, can be used for floor protection or even to take up some additional space if the thread isn't quite long enough. Talk about versatile! I don't know if May Audio still sells the BBC line, but if not then try Holm Audio who used to handle the line back in '99 as well. Both links are provided below. If that fails then contact me via email & I'll try to look up the manufacturer directly from my sets' packaging.
http://207.21.251.91/mayaudio/home.asp
May Audio Marketing
10524 Lexington Drive
Suite 300
Knoxville, TN 37932
423-966-8844
http://www.holmaudio.com
2050 West 75th Street
Woodridge, IL 60517
Phone: (630) 663-1298
Email: info@holmaudio.com
http://207.21.251.91/mayaudio/home.asp
May Audio Marketing
10524 Lexington Drive
Suite 300
Knoxville, TN 37932
423-966-8844
http://www.holmaudio.com
2050 West 75th Street
Woodridge, IL 60517
Phone: (630) 663-1298
Email: info@holmaudio.com