Here are the steps I took:
1) Download tubemate via tubemate.net. I found that the Opera mirror worked for me.
2) Open tubemate and search for 4K. There is a series by Jacob and Katie Schwarz. All of them are name xxxxx in 4K or something like that. My favorites are Costa Rica in 4K, Birds of Prey 4K and Wildlife in 4K.
3) Choose the download option, and select the second from highest resolution (2560x1440).
If you select the resolution that is higher than the Tab screen resolution it will stutter and not work well. 2560x1440 looks AMAZING and the clips are accompanied by good music.
COSTA RICA IN 4K 60fps (ULTRA HD) w/ Freefly Movi: http://youtu.be/iNJdPyoqt8U
WILDLIFE IN 4K (ULTRA HD) 60fps: http://youtu.be/xDMP3i36naA
BIRDS OF PREY 4K (ULTRA HD) 60fps: http://youtu.be/TN-pwblNxU4
Oh, don't forget this one: Myanmar (Burma) in 4k (Ultra HD) 60fps: http://youtu.be/DX48mJjL7oU
. It looks amazing and is actually really quite moving