Our cotton covers add very little to the original foam, if your glasses fit fine inside the original interface you shouldn't have a problem with our covers.
For the interface - it depends. If your glasses have thin arms and a relatively small width you should still be able to use the interface. However, those whose frames have bigger arms will struggle, especially as the plastic we use for our interface is more rigid than the original. Until we come up with a new modified interface for glasses wearers the best option is using prescription lenses