I've added a couple of numbers to raw_rec.c and now i'm getting around 490 frames (>20 sec) with 1200x500 (nice 2,4:1 aspect ratio). Stable, no pink frames. This is already enough for me to film entire short totally in raw workflow.
550d
1080p 24 fps mode
23.976 fps override
global draw off
Sandisk extreme pro 95 mb/s
p.s. I've added just a 1200 px to the list of resolution choices and my favorite 2.4:1 aspect ratio.
I guess there are much more aspects affecting resolution choices, like DMA cropping routines etc, but 1200 works for me.
upd. Latest A1ex's optimizations (speculative start) doesn't give me any performance increase (as he mentioned, they won't), but either doesn't produce any bugs or artifacts like empty frames etc.