You can make that a "tuckable" by adding reverse J-hooks made of Kydex. The Reverse J-hook is made by taking two 1X6 strips of Kydex, and bending the first 1/4" of the tip to form a "J" then making another bend in the same direction at about 2". Drill the other end and attach to the holster with Chicago screws (post screws.) Slide the whole holster between pants and skin, but let the J-hooks pass outside the pants, gliding over the belt. They will click into place, with the 1/4" bends under the lower edge of the belt.
Tuck the shirt between holster and pants, then "blouse" the shirt -- pull out 2-3" and let it hand loose all around.
