ric - my view is that with the speeds involved there is 'time' at 81kts to glance/shout/ask/grunt across the cockpit without imperilling the take-off/abort - and more often than not there are 'indicators of wellness' during the run up to 80kts, so the odds of a 'sudden death' at exactly 80kts must be remote? It will take a few seconds only and still leave ample time to stop on a 777 etc.