I'll take a wild stab at it (mind you, I haven't soldered anything together in ages). IMO, what happened is that Sony decided to make a series of cameras with essentially the same compact body. Once they decided to do so, their economy of scale production probably led them to put all of their A7 models into the same electronics scheme, i.e, most everything inside all models was wired the same way and, as long as it was 1080p, it all worked fine. Now, when they introduced internal 4K, they had to up the computational power in order to process a vastly superior amount of data and got backed into a corner because the internal layout of the camera wasn't especially conducive to the elimination and the passing of heat. Thereafter, they had the options that I surmised in an earlier post - a heat sink, a fan or some fairly expensive heat insulation (titanium, tungsten, ceramics, etc.) - which have their own drawbacks. And, I'll speculate again, they probably thought they found a reasonable solution to the problem. A7RII is heavier (625 grams vs. 485 for A7s) and slightly bulkier (127 x 96 x 60 mm vs 127 x 94 x 48 for A7s) and it almost does its job ... if your job is under 30m in duration. And, if it ain't, maybe there's a fix somewhere in its future.Here's what I don't understand. In my personal experience, neither the Canon 1DC nor the Panasonic GH4 have this 4K related heat/shutdown problem. Neither of them shut down after 20 minutes and need to cool off. I understand the the 1DC costs thousands more and is a good deal bulkier, and that the GH4 has a micro four thirds sensor. But a major selling point of the A7RII was supposed to be the internal 4K factor. I held off getting an Atomos Shogun, because I was really looking forward to shooting 4K on the A7RII like I do on the GH4 (without worrying that the device will overheat). 100 Mbps 4K (like the GH4) would have been more than enough for the talking head interviews I was planning on shooting with the A7RII. I don't mind the battery issue, but having to shut down the camera after 15-20 minutes to prevent it from overheating would be a major problem for me .