Frames in SDF robot model: how to define relative links?

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I just started writing an SDF model for a robot arm and I would like to define the pose of a link relative to another link, as opposed to the model frame. The SDF spec mentions both a frame tag (http://www.sdformat.org/spec?ver=1.5&...) and a frame attribute of the pose tag (http://www.sdformat.org/spec?ver=1.5&...), but I can't find any documentation or examples of how to properly use it.

Here's a simple example of what I'm trying to do that isn't working:

<?xml version="1.0"?>
<sdf version="1.6">
  <model name="example">

    <link name="base">
      <pose>0 0 0 0 0 0</pose>
      <visual name="visual">
        <geometry>
          <cylinder>
            <radius>0.1</radius>
            <length>0.025</length>
          </cylinder>
        </geometry>
      </visual>
    </link>

    <link name="link1">
      <pose>0 0 0.1 0 0 0</pose>
      <visual name="visual">
        <geometry>
          <box>
            <size>0.2 0.05 0.1</size>
          </box>
        </geometry>
      </visual>
    </link>

    <link name="link2">
      <!-- Want this to be relative to link1 -->
      <pose frame="link1">0.2 0 0 0 0 0</pose>
      <visual name="visual">
        <geometry>
          <box>
            <size>0.2 0.05 0.1</size>
          </box>
        </geometry>
      </visual>
    </link>

  </model>
</sdf>

However, this is the output (I'd like link2 to be at same z-height as link1):

Given that the frame information isn't exposed in the Gazebo Model Editor GUI, I suspect frame isn't completely supported?