Would it be sufficient to use three footers instead of four under a component?
Three is often sufficient. With most components and speakers, however, we usually recommend four. With four, you have more vibration-absorbing material in intimate contact with the component chassis to more effectively arrest the component's internal vibrations, areas of the component are more evenly divided for vibration control, you have superior lateral stability, more latitude with placement of the footers and most importantly, you'll usually achieve a sonically superior result.