I often used a “holster” made of 550 cord for the P7 to secure it below the belt line. Later I had a special kydex holster made for the 442 that I designed and was made by Frank Oleson to tuck the butt in and ride the but just above the belt line and it worked with a super light Eagle BDU belt to pull the gun in tight yet not look like a gun belt. That was in about 1998. The tucked butt kydex holster that was popularized by Custom Carry Concepts and essentially perfected by several makers today is not new, but technology and hard focus by several makers and users has gotten us to some exceptional designs.
I currently use very AIWB specific kydex holsters from Keepers Concealment, JM Custom Kydex, Dark Star Gear and Phlster. For very deep concealment and undetectable carry with neatly tucked in shirts my current go to guns are modified Raven Vanguards for a custom Glock 43 with a 48 slide built by Boresight Solutions or a custom S&W M&P 340 with a Titanium cylinder. I want to point out that a drawback to kydex holsters is they are hard. If getting bump searched is a reality in your world, leather is a very good option.