If you set your intervals to 1/2 stop instead of 1/3 stop then you'll get 1/180. Not sure if it's worth the hassle though for an extra 1/20.
Curious though, have you tried firing at 1/200? I just realized that I haven't pushed it to see how far I can get away with. My 400D never bought me much, but I've heard of people having luck pushing past the max sync on other models.
Thanks for the tip! That works, and yeah a bit of a hassle for not much gain, but worth doing when working with strobes outside where every little bit helps.
I have tried shooting at 1/200, and I get a small black band at the bottom of the frame. So sadly it doesn't seem possible.
Good to know. I use RF-602s, so I didn't expect to push it with those, but it was worth looking at. That said, often the small black band isn't an issue in non-studio situations (i.e. foreground lit by ambient). I've even pulled the 'flip the camera upside down so the black band is in the sky' technique and pushed it to 1/250 with my 400D.