Ok cool, I'm doing some high speed sync flashing lately with the MM, love it, but flashing on max output is a drag sometimes. I might go for the newer ones soon. Might be cool to try that new system. Cheers.
Even with the new ones I get best results with full power, it's just part of how it works, the longer the flash duration the more of it you see in the shot. I don't know about Canon but Nikon's shutter curtain speed is constant, so while your your exposure time gets shorter when you increase the shutter speed, the time from the start of the exposure until the end of the exposure is pretty much the same between 1/1000 and 1/8000 if that makes sense. And as soon as the duration is quicker than that you won't see the flash in part of the frame. I wish I had some slightly more complex testing equipment...
You can use the high speed fp sync feature on your 7D with dedicated Canon flashes. Range is pretty limited without something like a Pocket Wizard or Radio Popper to turn the infrared signal into a radio signal, and your power output is greatly reduced. But it works great if you're shooting close and wide and you have a TTL cable...