My trial of the Harrows "Silver" Short Titanium stems didn't go too well. They were too short for me, so I'll have to try the Medium ones to give them a proper airing. The short length caused inbalance on my 27g 5cm darts, so as mentioned I'll need the longer version to get a fair result.
Until then there are just a couple of observations ; some of the stems I received were not perfectly machined and did not spin "true" in the hand, so for every couple of packets you may need to bin the odd one. Also, the thread on the stem to attach the flight holder was incredibly fine and I'd prefer a chunky thread. I just didn't have confidence that these replacement tops would survive any sort of serious punishment with such a fine thread.
One very surprising positive is that you get a nice reflection on the dome part of the stem which acts as a strong guide for subsequent throws. I find this really helpful, as it allows you to concentrate on the throw and block out distractions. No other stem I've tried gives this type of reflection.