I did hear back fram Dave. He said there is enough metal in the grooves of a Spy to machine it for trits between the slots of the rail adapter area.
Dave designed & manufactured the Spy, knows it better than anyone else on earth & has the fixtures already built to hold the body. My suggestion is to send the light to Dave & have him mill the slots.
The Spy is a light that I will not modify in any way.I wouldn't try it on my own light & I certainly wouldn't try it on yours.