Travis I'm literally in the middle of a series and I don't have th ability to set up a camera with CFAST cards to test.
I know that CFAST has always been reliable to me. I haven't lost shots.
The only time I have it stop recording on the 12K is sometimes when I am using the Q1 setting on a single card and using a very wide lens at deep stops. The Q series vary compression by HOW MUCH IS IN FOCUS. In theory Q0 will max at a higher data rate than constant, however this rarely actually happens, and if it does is usually momentary.
There's no setting I can't shoot once I go to dual cards in Q series in my usual on set work, without me doing the specific work of studiously testing media. I did this early on but it's meaningless to compare because my numbers are with pre-production units and different iterations of BRAW.
I know also that you CANT just take the manufactures specs on ANY cards or any media as being the (whole) truth.
There's a lot of stuff going on underneath the hood that affects the performance of media. The sustained media numbers are simple MARKETING numbers for the media, and are typically generated but the manufacturer in different, usually more idea conditions. No media maker "test" their numbers with a 12K camera recording continuously. It's not JUST the data rate. It's the way the data is moved around. It's only an INDICATOR of performance in general conditions.
(EDIT even this post proves this
viewtopic.php?f=2&t=137309&start=50#p748529)
I also know that my friends at BMD have told me the fastest card that tested WITH THE 12K when I was doing early testing was the Angelbird 256GB. Other Angelbird are also very good too.
A CFAST card is not that expensive in the context of a 12K. The best thing for you to do is to TEST the cards in your use scenarios. I've mentioned this to many threads. Go buy a couple of cards and use them for back up if you need. Just do it. Don't listen to me, or what others say. Go test it for yourself.
I've even used my Sony SD cards at Q5 successfully when I needed to.
I want to also say that many of us here did say that the problem with USB media is the EXACT problem you had. Here we are with all of that only strongly confirmed.
I understand you WANT to use the USB based media, I know the cost is an issue for you, and I understand you're looking at the specs and trying to make sense of it all.
CFAST media makes all of this go away. Take away the angst...
JB