Timeouts testing polymer elements with web-component-tester and sauce labs

Question

We're having trouble testing our polymer elements with web-component-tester and Sauce Labs. When we try to test with more browsers than our subscription level allows to run simultaneously, the tests that don't run immediately eventually time out. It seems really wrong that sauce labs and/or WCT doesn't know how to wait to begin executing a test until the other tests are finished, so that we can queue up as many tests as we wish without having to worry about VM utilization.

Has anyone figured this out? Thanks.

Here is our wct.conf.js in case it helps:

module.exports = {
  testTimeout: 600 * 1000,
  persistent: false,
  ttyOutput: false,
  verbose: false,
  expanded: true,
  browserOptions: {
    name: "TWT Component Tests"
  },
  suites: [
    'elements/twt-elements/test/index.html'
  ],
  root: 'app',
  webserver: {
    pathMappings: [
      {'/secrets.json': '../db/secrets.json'},
    ],
  },
  plugins: {
    local: {
      disabled: false,
      browsers: ['chrome', 'safari', 'canary', 'firefox']
    },
    sauce: {
      disabled: false,
      commandTimeout: 600,
      idleTimeout: 180,
      browsers: [
        /* see https://docs.saucelabs.com/reference/platforms-configurator */
        /* support matrix: https://docs.google.com/spreadsheets/d/1XqTxODsi2s2GGllld1yHImtb-2ubCX1XbRsvZ4DqpZI */
        {
          browserName: "chrome",
          platform: "OS X 10.9",
          version: "40"
        }, 
        {
          browserName: "safari",
          platform: "OS X 10.9",
          version: "7.0"
        }, 
        {
          browserName: "safari",
          platform: "OS X 10.10",
          version: "8.0"
        }, 
        {
          browserName: "chrome",
          platform: "Windows 8.1",
          version: "40"
        },
        {
          browserName: "internet explorer",
          platform: "Windows 8.1",
          version: "11.0"
        },
        {
          browserName: "firefox",
          platform: "Windows 7",
          version: "27.0"
        },
        {
          browserName: "internet explorer",
          platform: "Windows 7",
          version: "10.0"
        },
      ]
    }
  }
};