At the 2014 International Technical Rescue Symposium (ITRS) held in Golden, CO, Kirk Mauthner presented his research and demonstrated a number of drop test using a 440 lbs. (200 kg) load. These were over a 90-degree sharpened edge, from various heights and different types of edge protection.
Mauthner’s concluded that there was no apparent benefit in using a single tensioned mainline (STM) and un-tensioned belay (UTB) over a two tensioned rope system (TTRS).
The same holds true today.