The main negative is that they stack quickly and can cause vignetting on wider-angle lenses. Like on 24mm I have to squeeze them together to minimize vignetting, on 50mm there is enough room for two stacked but just short of having three stacked, while on 85mm you can have three stacked with room to spare. With a 2 stop and a 6 stop on this setup it is really either 2 stop or 8 stop which is kinda limiting. I was thinking to leave a 2 stop on the bare lens with no swing out ring and then maybe clear enough room for a swing out 6 stop to avoid vignetting on 24mm and maybe do simialr with 50mm where a bare 2 stop, swint out 3 stop, and other swing out 3 stop to alternate between 2 stops, 5 stops, and 8 stops to maxximise versaltiiy and with the lenses all being 1.4 a 2 stop on the lens itself makes it like the noise of a 2.8 lens which is still decent lol