I looked over Slee's instructions, but I'm not clear on what all I have to do to get this bugger to fit. The radio seems to be about 1/4" too wide for the ash tray holder. Also, do I need to trim down the two screw mounts on the dash below the radio, because I can't see how this thing is going to fit without cutting off those mounts 1/2 way--to the point that I won't be able to get a screw in there again. Is the 520 bigger than the 510 or something?