I have one of the Null rigs (SMZ). I agree, they are fine for low weight applications. But, they're not a "beltless" style. I've altered a few shirts to have a hemmed opening on the R/S seam above the belt line, sort of like an enlarged button hole. This is required, to allow the off side support strap loop to pass through the shirt and be installed around your belt?
Another method I use, though rather slow is this product....

Kramer Handgun Leather: Revolver holsters, concealment holsters, paddle holster, 1911 holster, ankle holster