I have 2 sets of the LaserMax J grips and this is the first time I noticed that they are only for round butt pistols. I think that short of modifying your square butt to round butt configuration, you won't be able to use the LaserMax grips on your pistol:
http://www.lasermax.com/installation...uide_(web).pdf
B-Square makes a laser mount for the J-frame pistol that mounts via the side plate screw and places the laser under the barrel. What results though is not very sleek, and looks like it wouldn't hold up well to the bumps and bruises that a carry gun gets.