Best way to go is to build one yourself. Forget about the crappy DJI frames and get something reliable. Lots of frames out there. My advice is to forget the other two cameras and build around the GH4.
As with all DJI products you should wait for the "Mark ii" versions since the first ones are always beta testing. I am proud to announce that I haven't bought a single DJI item for over a year.
Some guides that might help.
http://wolfcrow.com/blog/davinci-resolve-crash-course-for-beginners-part-one-setting-up/
http://www.colorgradingcentral.com/blackmagic-camera-tutorial-series
Before installing the Herkules board I used a spare center plate on standoffs to shield the esc installed on top. I believe on top is cooler for the esc.
http://www.multirotorforums.com/showthread.php?6886-DJI-Wkm-and-Herkules-III-arming-issues
My Skyjib X4 can hold my body weight and not brake. 70+ kilos. I tried... My opinion is that the motors you have will work fine. DJI fc's like hovering above 65% max throttle.
I too miss the days spent training my soldering skills before messing up a tiny electronic part. Plug n play is nice but you don't get the same feeling of achievement when you are done.
About a year ago I converted my SJ8 to X4. It is better all around and the size is more manageble. Almost the same flying time. What I find makes the biggest difference is the esc you use. Fast esc work much better with DJI fc's. I use Castle Ice, Ultra esc and Herkuless III on my main...
I would also check if your motor mounts are level and recalibrate the esc's. Something to consider is to flash your esc with simonk code if possible. Try your next test flight with 1 kilo weight more.
No need with all the people rushing and pre ordering DJI's beta crap. With the sales going strong no wonder they don't take the time to debug the code any more.
7.4 kilos. No issues here. Can't say the same about 4-5 brands of cheap esc I crashed with. I did extensive research before geting the CC esc and I knew about the issues the high voltage line was having. But I am not running a 12S Heli with them.
No issues at all for over a year with my Ice50. Only running them on 4S with MT2814. Performance is much better than simonk flashed junk esc.
Some other good options are the Ultraesc and the Herk III. All 3 esc have performed flawless for me for many months.
Cheap esc's and lipos is one of the...
A safer, cheaper and "saner" option is to just use what you have and buy a Black Hero3+. For stills you don't need a large copter. A QAV500 can get the job done.
https://www.youtube.com/watch?v=EeLZr6zRh0w
+1
Having volt, amp and mah consumed is a necessity for me (MUI sensor). If I remember correctly only the early batches had the free R9 in the box.
http://www.multirotorforums.com/showthread.php?6979-Jeti-DC16-unboxing