The difference between Firewire 400 and 800 is 2 pins which are used for power supply. I don’t think the MR816 even works with buspower, so 400 should work just fine. (adapter will work, or you can get yourself a new cable, I dislike having big plugs as they easily break the socket if you accidently hit it.)
I don’t know about the specific combo you mentioned, but generally if it’s a TI firewire chip you should be fine.
i use vaio f13bfx… i bought a Good FW cable for my vaio which uses the small connection.
after some twiking and using the ysfwutility utility its working preety well.
*for me to work with mr816 i turn the wifi off
*disable devices i dont use…(card readers,bluetooth,Lan,nvidia audio drivers etc…)
*disable services i dont need and optimize win7 64bit that came with vaio.
*also in bios i disabled c3\c6 which reduce my dcp latency to 150…
*i use the legacy driver for the firewire controller.
*** at first the only thing that could work for me with mr816 was to use standart VGA for display adapter(to reduce dcp latency to normal and working state) but now im not sure why, i can use the Nvidia driver as well(maybe after nvidia update or c3/c6 off not sure)