If the OP is experiencing "stuttering" on his computer I'm going to suggest he has a computer problem. having a slow computer and trying to play back UHD video and experiencing issues is a very common problem. If he wants he can download a video shot and processed in 4k that has zero stuttering issues to help determine if the problem is the video or the computer. I have a couple of car show videos that can be viewed on Vimeo, where you can adjust the video quality by using the gear icon at the bottom right side of the media window. If you experience "stuttering" change the video quality downward until the stuttering goes away. Both can be downloaded. Both possess a Creative Commons license with attribution and no derivative requirements. One was shot and processed in 1080with an H and CGO-3 and the other, longer video was shot and processed in 4k using a 920 and CGO-4 camera. Neither provides any level of "stuttering" unless either the internet bandwidth available during online payback is limited, or if the computer is too slow and lacks the graphics card and/or screen resolution necessary to handle them. Give them a go on your computer and see what happens.
Typhoon H/CGO-3, 1080 video:
920/CGO-4, 4k video: