It's been talked about before, I just can't find the thread.
Evidently the Burris magnifier has a raised lip on the front of it that won't let it pass through the L/T flip mount. Pretty sure L/T said to put a dime in the slot at the top of the mount and screw in one of the screws against it. This will spread the mount enough to get the magnifier in, then remove the screw so you can pull the dime out and tighten normally.
I would verify with L/T though, if you get hamfisted spreading it and go too far you may do some damage.
edit: Found instructions for ya, on of all places Burris's web page.
http://www.burrisoptics.com/laruemountkit.html
AR-Tripler™ Installation Instructions for the
LaRue Tactical Pivot Mount
The Burris AR-Tripler has a 30mm mounting area but also a 30.7mm
objective bell. This requires the LaRue mount to be opened to get the objective
bell through the ring. To facilitate this installation, a Jack Screw has recently
been added to the Burris Tripler packaging and is available at no cost.
Insert a dime into the gap in the top of the ring. Thread the longer Jack Screw into the threaded side of the ring as shown. Open the ring until you can slide the objective bell through the ring opening. Unscrew the Jack Screw, remove the dime, and install the original LaRue ring screws.