I have a Kenco 3xTC which was marketed as for manual use but it works in AF on the R5 as well as in liveview on some DSLR bodies. As it was a reasonably clear winter's night and half moon, I paired it with a 2xTCIII on a 400mm DO II on the R5 and took a shot at 2400mm, f/24, 1/125s iso 1600. Vanilla DxOPL4 plus Clearview to enhance contrast. I had to downsize by a factor of 3 to upload! A couple of full-sized crops included. A challenge to the 800 f/11!