I've only got a Driving Force Pro here, but it's the same mounting mechanism. I just measured the maximum span and it's 50mm.
The G25/7 might be different, you should see if you can find out, maybe another forumite can check for you.
Bear in mind that even if the gap on the G25/7 is 50mm you might be able to find that missing 10mm from somewhere. Maybe by butchering your desk or butchering the wheel. I seem to remember Tristan, years ago, taking a hacksaw to a Logitech Momo wheel to get it to mount on a particular desk.