Here is the US Duty Gear Glock 17 holster made to accept WML and slide mounted optic. I have the Safariland QLS fork installed.
For some general comparisons of size, ride height and protection of optic, I am including pics of the Blackhawk! T-Series. The T is shown with the 10-8 adapter plate installed. The plate converts the T to the QLS system. It should also allow the Blackhawk! to work with the Safariland UBL directly if someone wants more versatility in ride height.
Safariland low belt loop used.
QLS forks on both holsters. Again, the 10-8 plate is used for the Blackhawk! No plate or any sort of adapter on the USDG holster.
Holsters on belt. Note location of backstrap in relation to the top of the belt.
Optic coverage. The Blackhawk! has a locking cover that locks into place via the rotating hood. The USDG is more open and does not provide a cover for debris, etc.
Stand-off from the belt. The Blackhawk! sticks out quite a bit especially with the 10-8 plate in between the holster and fork.
Lastly, my Shadow Systems DR920. Just because it is cool!
BTW--both holsters fit fine with the TLR-1 pressure switch attached.