I think the spikes w/decoupling gliders will give you the best combination of decoupling, leveling, and mobility. The flat feet probably don't decouple as well as the decoupling gliders. You could place Big Fat Dots or Decoupling Gliders under the flat feet, but that might be a little awkward.
If you like a lower profile better, using Herbie's Little Fat Gliders or Giant Fat Gliders instead of the flat feet or spikes would likely be an improvement, but you'd lose the leveling ability. Using sets of three would alleviate much of the leveling issue, though.
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