The no drill mounts for the sp101 are only compatible with adjustable sight models. I had a fastfire iii mounted on my 3 inch sp101 in .327 federal earlier this year. My gunsmith was able to mill the no drill mount to match the flat of the top of the frame, then he drilled and tapped it. This is about as low as you can mount a red dot on such a small revolver. I haven't shot it much yet but my first 6 shots out of the gun at 10 yards was about the size of a 50 cent peice. It takes some tinkering with grip and presentation to find the 3moa dot quickly, but the degree of precision that it has added to to my sp101 is pretty awesome.
Did you know that there are magical animals roaming wild, converting vegetables into bacon as we speak?