Help with mounting a TV on a wall in my house...will my wall mount work?

I have a 60" plasma TV, with a total weight of 67lbs.

I have an IXOS Overture XHM444 wall mount (very well made) rated for up to 46" and 165lbs.

So, I am way under as far as weight, but will be above the maximum size. The mount will fit the mounting holes on the back of the TV, but the screws will be at the very edge of the mounting arms.

Here is a pic of the mount:
XHM 444 IXOS Fixed and Tilt Bracket SPECIAL OFFER 32" 37" 42" LCD/PLASMA Wall Bracket

What do you guys think?