(My first post with pics...bear with me)

I've found a source for a picatinny rail for the model 15. The attached pics will show that my gunsmith mounts the rail to the vent rib only, not the frame. The rail is cantilevered over the frame, back to the rear sight. Clearance between rail & frame, at this point, is .007. The appeal of this arrangement, imho, is that I can change barrel lengths, and the rail and scope stays with the 6" assembly. The rail can be removed from the vent rib, and two filler screws can be inserted to fill the holes, with no interference with the sight plane. If you want more info, call the gunsmith, (he  gave permission) Sean Fraser, at 817 705 8671. Good Luck