Well, guess it's a no-go on XS sights for a Sigma.. Got the word back from Bo Wallace at XS..
"Sorry but the SIGMA sight cuts are their own unique size and shape.
Back when the SIGMA first came out we did make sights for it, but after a couple of years demand ceased and about 3 years ago after several years of no sight requests for that model we discontinued them and have none left in stock. In the last year we have been getting the occasional request for SIGMA sights. I will put down yours and if this keeps up we will add them back into the line. All I can say right now is check back at the end of the year."
Bo Wallace
I know it's a moot point, but why would S&W put some unique size/shape cuts in the Sigma slide? Seems like making a gun "more" adapative to aftermarket sights, grips, etc. would make it more easily marketable.. Oh well, guess I'll have to live with the stock sights for now, although Im gonna have to find something along the lines of night sites here shortly, as I cant see the stock sights at all in the dark, and this is my only SD/NS (night stand) gun..