In principle, the holders work well. The flash is above only "pinched" between two metal strips, but that seems to be sufficient. Even if I had concerns when the flash may not be entirely without contact: that is, under studio conditions that is not a problem out there with the wind and weather, I would have concerns that the flash head from slipping.
The screws engage unfortunately in hard plastic. The experience has shown that less than optimal for continuous use. Better would be at the lower part towards Lampenstativ pure metal (above the hotshoe holder).
