Multiple ND Filters in Place of One Variable ND: Any Problems?

I have lots of lenses, of different diameters. Shooting in Slog3 requires a minimum ISO of 640, which means in bright light, shooting at 30p and obeying the 180 rule, I have got to use ND filters. I recently acquired the Sony FE 24mm f2.8 G lens, which is a really small lens to complete my tiny rig collection. I need to apply an ND filter for it, at 49mm.

Yes, I could use my 77mm variable ND and a bunch of step up rings, but putting a 77mm VND on a lens with a 37.5mm (the Sony pancake 28-60mm zoom) or 49mm diameter makes for an absurd and non-ergonomic rig.

And, many complain about the quality of VND's, even the expensive ones.

So, how about using multiple ND's on one lens? For very bright light, use two; for shadowed areas in sunlight take off one, etc.

So, I tried using two 3-stop ND's on the 49mm diameter lens shooting in bright sunshine. This permitted me to use wide apertures and achieve a shallow DOF when I needed it. To avoid vignetting, the second ND was 52mm, mounted on a 49-to-52mm step-up ring.

Here is the result (which looks fine to me):