Hi, On Facebook I saw that someone used both tele-converters (1.4x and 2x) together with 400mm f / 2.8 via Kenko extension tube 16mm. Extension tube served as a bonding device between teleconverters. So he had on body TC 1.4x + Ext. Tube 16mm + TC 2x + 400mm f/2.8. AF worked and there was no significant drop in image quality. So he had 1120mm lens. I wonder if a combination of TC with extension tube and a 90mm f / 2.8 G OSS lens would work similarly. What do you think? Can anyone try it and let me know?