I picked this up and have been testing.  The assembly looks a bit frankensteinish but seems to serve the purpose.  I agree with CatAreGods comment on this maybe being unnecessary under some circumstances.  I am pretty happy with it from the standpoint that it lets me balance the entire camera/lens/teleconverter assembly much better over the tripod mount.  That will come in handy with windy or other challenging conditions.

I'm going to throw in my two cents here. I have the Fuji GFX 50r and the 50MM pancake lens. This is a great street and general shooting 1-lens kit. As to the difference between FF and MF, I also agree with Jim, I see a difference in the color and resolution on screen (I have yet to print from my Fuji yet). A friend refers to this characteristic as the "special sauce," the combination of Fuji's sensor and lenses. Yes, I have FF Canon R6, the files are good, but there is a visual difference that to me looks richer with the 50r.  The shot of Mano was taken with the 50MM lens on the 50r.

Nope, even when it was at minimum extension, no hood.

Thank you for your all your replies. I'll update this once available. It's not easy to go to the service center this time.