Here is a classic pillow shaped project foot. The files below include a single of the 20mm and 15mm square base, plus a 4-up file of the 20mm size. The 15mm version was an after thought. I tried doing a 10mm sized foot, but it printed poorly (not sure why, probably some SkeinForge settings).
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Imported from Thingiverse: https://www.thingiverse.com/thing:3491
Original creator: ElectronicKit