Thank you Steve for sharing your findings with the R5 and 100-500. I too had a very similar experience with the rental I had. The files were amazing and as long as I did my part, they required very little post processing. Just to confirm my findings, I rented the A1 with 200-600 again, and I agree the R5 with the copy of the 100-500 I rented produced amazing images. They were my favorite images I've taken all summer. This may sound silly, but I can't tell you the number of times I've looked at those pictures over and over again that's how much I fell in love with the quality. And to be honest, for me, the 7.1 and the issue with adding a tele weren't ideal but not deal breakers. I also was amazed at how much detail was retained even with excessive cropping. Not something I like to do, but wanted to test out. My issue is with my ability to follow the birds when using the ES 1st curtain over the ES since I have a lot of erratic action that often has vertical lines. All said, if that lens was available today, I would purchase it in a heartbeat!
I hope you, or your wife, will share more thoughts on the R5 with the 100-500. Many thanks to you for all that you do and to Backdoor Arts for sharing his experience and journey moving from the D500 with PFs to the R5 with the 100-500!