One issue with the DeSantis SofTuck and TuckThis II series of IWB holsters is the belt clip.
The belt clip actually goes over the waist of the pants and behind the belt, with a small upward piece that grabs the belt from below, holding the DeSantis holsters in place while the weapon is drawn. While very concealable, this design puts the weight of the pistol on the soft fabric of the pants waist rather than the more rigid belt, like better designs. The problem is that even with small lightweight pistols such as the 709, 740, LC9, and Shield, the waist on the pants tends to droop under the weight of the pistol, with the bottom edge of the belt clip actually being substantially below the bottom edge of the belt.
This DeSantis belt clip is sometimes referred to as a reverse "J" clip, with the body of the "J" behind the belt, and the bottom of the "J" being where the bottom edge of the belt is supposed to sit.
Some makers make a similar concealable belt clip called a "C" clip, where the belt goes through the "C", with the back of the "C" being behind the belt, and the top and bottom of the "C" bracketing the belt; this "C" clip is almost invisible when worn, because the belt is what shows, not a metal clip.
High Noon uses a "J" clip that goes over the belt, and then turns up under the belt from the outside; this is very secure when drawing, and puts the weight on the stiff belt. When using a wide black belt, the belt clip is well camouflaged black on black.
Some other common belt clips, sometimes called "K" clips, go over the belt and secures like the "J" clip, but then turns outward with the bottom edge of the belt clip facing outward. These are easy to mount and dismount from the belt, BUT have a reputation for snagging on upholstery; more than one car seat has been ripped when someone with an IWB holster with this type of belt clip slid into our out of a car. Some people plastic coat or electrical tape the sharp outside edge of the "K" in order to minimize the chance of upholstery damage.
Holsters such as the Remora and Sticky (stickyholsters.com) are clipless and depend on a high friction surface to hold the holster in place. While videos show users doing acrobatics with the filled holster staying in place, there have also been several documented cases of holsters sliding down a pants leg or otherwise shifting.
Good luck!