I'm renting the R for a week to check it out prior to considering buying it. It would be my first FF camera. I shoot wildlife and always use a crop for the distance factor because I can't handle the weight of the FF equipment for the places I want to go and the things I want to do, so that's the compromise and it's worked well so far, but the size of the picture from the 7DMII and the quality in low light leaves me increasing frustrated when I compete against other FF competitors. I try to do more artistic/unusual/behavioral wildlife composition and capture unusual lighting rather than things that demand maximum high speed but that's not to say speed and capturing the decisive moment isn't important. I'm used to shooting at ~150-600 equiv range to get the pictures I want. Has anyone used the R with 1.4 TC and the 100-400 II lens? How did it perform for single shots?