The 507K doesn't hang over and looks perfect on my SP-01T and PCR.
I didn't realize the Shadow slides were that much wider and agree with Born2vette, a bigger window is better if concealability isn't an issue. I use the SP-01T for competition and wish I went with a bigger window.
The solution is now obvious. I need to buy a Shadow but will prob go with the Carry model as I prefer de-cockers.