Found a pre owned Fuji 2.0x converter at a good price which overcame my initial indecision over purchasing one new. I have been trying it out on a Fuji 70-300mm zoom with quite pleasing results. I have a feeling that the main benefit over my 100-400 + 1.4x will be a weight saving which as time goes on, seems to become more attractive.

X-T4 70-300 + 2.0x
European Brown Hare.

European Brown Hare.