I'd have to agree with Terry. A call to Canon might help.

Test results
 

Ok, took a picture of the cams viewfinders at 1 min and 34 min and they showed the timelines stayed in sync, off exactly 2 seconds from camA to CamB. However when put on the timeline synced the flash at 1 min and 34 min and camB is 2 seconds ahead of camA I counted the frames and its 59 frames.

Is this typical or acceptable in 34 mins of footage. To many people this may seem like a simple thing but when your trying to keep peoples lips in sync with the audio from a different clip it can be a pain. It can be fixed, it would just be easier if it were in perfect sync.

Denny,
This is within the realm of small errors. Do the math. If in Sync at the start the cameras will crank out 30x60x34=61,200 frames in 34 minutes. A .001 variance in speed will give you a 61.2 frame difference over that time. .0001 difference still gives you a 6 frame difference. Even a .00001 difference will give you over half a frame difference in 34 minutes. If the cameras are Genlocked then they will run at the same frame rate eliminating this difference. Still might be adjustable in service but if not then you will have to deal with it in editing.

I appreciate your comments - every day needs to be a learning experience and since I don't do weddings (in fact, I've only even BEEN to five weddings in my 60+ years life - and two of those were my own, in front of a judge with only a handful of people, over and done in 15 minutes) you've stimulated some thought on how one might approach such a project. I was thinking in terms of editing for a dramatic piece where you'd show the departure of a character from one location and his arrival in another but cut out the intervening travel time unless something happened that was critical to the story or you wanted to establish a certain sense of psychological time in the mind of the viewer. In wedding terms that could mean showing the bride starting down the aisle and her arrival at the alter but cutting the rest of the walk other than emotionally significant moments like, say, exchanging a look with her mother. And I would have definitely thought you'd cut the long runs under green except for the moments surrounding changes in position, distilling the event down to its essence, the extreme example being "A Man And A Woman" where the whole 24 hours of Le Mans is distilled down to about 10 minutes of screen time.

As Daniel said - that's why higher level broadcast cameras have Genlock capability. Properly synchronized multi-camera coverage, especially with double-system audio, requires that all the devices to have their clocks slaved to a common timebase. Heck, even single camera coverage with double-system sound is most reliable with a common timebase to lock the camera and audio recorder's sample clocks together.