Whortleberry wrote in post #16115166
... The only
decent fabric grid I actually have is the one for the Cheetah / Godox 19" multifunctional softbox - and even that isn't
perfect. Most of the others are about as much use as a chocolate fireguard and roughly as floppy too.

Truly excellent fabric grids are available but at a price most photographers, hobbyist photographers anyway, are unwilling to pay. The grids from Lighttools, the fabric grid patent holder, are exceptional. Here's a 40-degree Lighttools grid mounted on my Elinchrom deep octa:
Apart from cell size and depth, one of the major problems with Chinese fabric grids is weight. This is a particular problem with the ubiquitous folding softboxes and their generic mounting brackets. The standard issue mounting ring (like the one on the front of the QBox bracket) has just about reached the limit of its ability to hold the attached softbox square to the flash.
Now, with a rubber ring applied to the circumference of the mounting disc, the brackets can support a 24" square folding softbox with a grid installed without sagging appreciably. The 30" is more challenging.
Early versions of the 30" folding softbox were rejected due to their weight. When mounted on the standard bracket, the front of the softbox would sag like Justin Bieber's pants. While the current version of the softbox works well with the standard bracket, I suspect the added weight of a front-mounted 30" x 30" fabric grid would cause problems.
In my view, the generic folding softbox mounting bracket is long overdue for a redesign. Lastolite recognized the problem(s) and redisgned their mounting solution long ago.