Yeah...generally this has been my surprising conclusion as well, that CFE cards are well below their listed performance. So, all of the theoretical calcs that those of us do, myself included, using the list specs are somewhat erroneous.

Hopped back to this thread as Camnostic has updated their review, for those interested. I still prefer what SSDreview is doing, but Camnostic reviewed specifically ont he R5, so some relevant data there.

Overall, having now shot on the R5 for ~18 months, what I can say is that I cannot recall ever hitting my buffer when writing to the CFE card (I have Sandisk 128 GB/512GB cards). But I have hit it when writing to the UHS II card slot. My solution has been to write only to the CFE card when shooting anything at high FPS and then copying over to the UHS card when I have a down moment. For lower FPS action, I write to both cards simultaneously.

So, while CFE cards do not perform at their spec, even when transferring files, they are still more than fast enough for my needs. The Sandisk CFE cards do get hot. If I was to buy another card, the operating temperature chart would get some of my attention, in addition to speed. This may seem odd, but after transferring files, the Sandisk cards are hot enough, I let them sit before reinserting into the R5. They can also be very warm when pulling from the R5.