STUMPJMPR: I had pretty good luck using J-B Weld to attach a Williams rear sight to an old 870 barrel. I soldered the steel front ramp, but the Williams base is aluminum, and so far, J-B Weld has held up to a lot of pounding from slug recoil (better than me, that's for sure!). I get best accuracy with Federal Tru-Ball slugs in a cylinder bore. Let us know what round works best in your gun.
P.S. . . . I have shot a few slugs in a 28" Pardner. The recoil is nothing to kid around about . . . it occurs to me that your 18.5" Pard is gonna kick you just a little bit . . .