I can't find any examples of people using ITW Fastmags in IDPA. Does anyone have any information as to whether they are allowed or not?

Thanks!

They look like they'd be legal.  They also look like they'd be slow.

8.6.2. Magazine Carrier Rules - Magazine carriers must:
8.6.2.1. Be suitable for concealed carry and all day continuous wear.
8.6.2.2. Must be worn on an IDPA legal belt.
8.6.2.3. Cover 2” of the magazine as measured from the top of the cartridge rim down the back flat of the magazine tube.
8.6.2.4. Cover the entire outer face of the portion of the magazine inside the carrier. The outer face is the side away from the shooter’s body.
8.6.2.5. Hold the magazine within 10° of vertical relative to the belt. (80° to 100° relative to the belt).
8.6.2.6. Magazine carriers with screws or knobs that extend past the outer face of the carrier are not legal.
8.6.2.7. Magazine carriers must be worn in a belt location where the front edge of the carrier or magazine is behind the shooter’s anterior superior iliac spine (hipbone).