5D mark II - sRaw2 file size strange.
There is nothing strange going on. You have simply mixed up MP (megapixels) and MB (megabytes). The 5DII sRAW2 is 2784 x 1856 (5.2 MP) but the file size (disk space used) was 13.2MB.
I have 5D II and set to sRAW2 (no "+" jpeg)
based on menu, sRAW2 is 5.5MB size, but when i shoot and check info of picture, it show 13.2MB
Why file size is double?