Created front attachment pass-thru slots by drilling 5/32" holes at end of each slot profile followed by free style "routing" using my old Dremel.
Tip: Hold Dremel bit at about a 45 degree angle and use light pressure. In Images 2 and 3 you can see the oversized hole that was cut when the bit caught the edges of the drilled hole and decided to walk around the perimeter. A slight cosmetic imperfection that could have gotten much uglier.
Finised slots with a small round file, flat file and deburring tool.
