TM8 for multi user massive mimo

It seems that TM8 is not pushed a lot in case of multi user beamforming. I would expect that dual stream would be better. It give higher user throughput, and at cell edge it can use two stream for a form of transmit diversity. Still I do not see a lot of beneefits provided in documentation. It seems that TM7 is preferred. I have not yet any experience, but we want to have more multi user beamforming to increase capacity. Is there anything to say on performance of TM8 in multi user deployment?