I am interested in hearing any feedback regarding the use of the Glow Bowens Low Profile speed ring insert for softboxes. From what I can gather it is @1" (25mm) deep compared to the standard issue 1.5+" (40-43mm) and gets the flash tube further into the softbox. The question is, does it make a positive difference in dispersion from the flash tube and better output.
Light effect will depend on the specific strobe, bulb and modifier. More diffusion will lessen any differences.
One issue to watch out for with "low profile" Bowens mounts is clearance on the back of the modifier. Thumbscrews on the back of the modifier can be taller than the speedring which will prevent the light from locking in place. You may have to DIY different mounting hardware.