. ....... will 5D Mk II and CF overheat during continuos work?
Short answer ; No
The thermal overload is around 75-80°C if I remember correctly (when the camera shut down to protect itself)
When I do development on the 5d2 (crop_rec & others thing) I stress the cam to it's limits
with liveview manipulations to a point where the camera no longer response 68°C & above

But the normal operating range in 10bit HD (1856x1044 @ 23.976fps with "
kill liveview on recording start" enabled)
35 -55°C (depended on the temperature of your environment e.g. +20°C or -10°C)
I wouldn't be
alarmed it the temperature increased to 65-68°C (still safe but may see a few hot pixels or more noise then usual)
FYI ; the new 48fps (1856x774) preset in the crop_rec reaches up 63-68°C as normal temperature operating range .
If you do use h264 , there is a "Movie Restart" Option , drops 1-2 seconds before it starts again , but they can be offset by staggering the start
of multiple cameras . If you do this option , I would recommend setting the h264 bitrate to 1.4 (if the card is fast enough) 65Mb/s to 90Mb/s (depending on camera picture style profile)
High contrast scene will have higher data rate then low contrast scene (50-75Mb/s) If you use "Technicolor CineStyle" Profile the max data rate is around 55-60MB/s
but that a log profile , if you choose standard of neutral profile the data rate will be high.
The other option that you can use is the HDMI Signal , It's a 8bit 4.2.2 60i/24p uncompressed (1.5Gb/s 1500MB/s data rate) Next best thing to Raw Video.
True that is not full 1920x1080p (1650x1080) but is scales pretty nicely , I've used it on a few news stories a few years ago , I have a old (1st gen) atomos ninja hard drive recorder
Thou it not longer available any more I've seen the
Atomos-Ninja-2 is out there and cheap too , this one is $115.00 (usd)
HDMI Uncompressed(1.5Gb/s) really come very close to raw video , after I graded it a lot of people couldn't tell the difference .
By the way: is there SD_UHS support for 5D Mk II?
No , because it a CF card not a SD .
All that "SD_UHS" is just unlocking the firmware on the camera with SD card (d5 cam only)
on the 5d3 , SD card chip is a SDR104 & on the other d5 camera it's SDR50 .
So what is this ?
https://www.sdcard.org/developers/overview/bus_speed/index.htmlCanon in all there wisdom decided to lock the SD card bus to "
High Speed" 25MB/s v1.10
If thou it has UHS- I chip v3.01
50MB/s (SDR50, DDR50)
104MB/s (SDR104)
What about 5D2 & 50D ?
will there is two option open to them , Lossless compression (I'm working on it) & CF Card Bus over clocking (just started to investigate this)
a1ex had did some test a long time ago on 5d2 and had the CF card overclock for faster write speed.
So if Lossless works on the 5d2 as the 5d3 14bit lossless data rate will be reduce by 40-50 % so a 128GB card
could hold up to 70mins at 1856x928 2:1 A.R.