hardwood floors, area rugs, and spiked feet

We're putting in solid oak hardwood floors and have purchased decent quality oriental area rugs, one of which is going into my listening space to cover the flooring between the listening location and the speakers. The rug will extend under the speakers. So the question is, what to do to stabilize the speakers on top of the rug without the spikes damaging the flooring underneath. The carpet is pretty thick and dense; it won't do just to remove the spikes and depend on the speaker feet.

I need a method to somewhat blunt the spikes but still enable them to get down into the backing of the rug. It won't do to just round over the spikes; the weight of the speakers will still damage the flooring. I'm thinking there's got to be some sort of a combination of a disc and shallow spike setup. I looked in several catalogs but came up empty.

Surely one of you folks has run into this problem in the past?