Well, I'd tend to agree it is legal, but a couple of concerns.
The holster and gun must now be evaluated while being worn by the shooter, so it could be legal on one person and not on another. One problem crops up when a too-round middle causes the gun to slant too far our. Also, the entire front strap to the trigger guard must be above the level of the belt, which cannot be seen for sure from the picture.
IMHO, the Yaqui Slide type holsters are not the best for IDPA; the front sight tends to catch on the bottom edge of the holster unless drawn just right.
Have you looked at the Safariland 568 (paddle)/569? I have this for revolvers.
The most popular IDPA holsters for semi-autos are the CompTac and Blade Tech.