I read an article on military times a couple months ago about a Safariland ALS holster designed to accommodate Glocks with red dots mounted. I had been wanting to try the ALS system after using the SLS roto-hood system for 10 years and compare the two for speed and ease of use. So I ordered one direct from Safariland customer service and 4 weeks later it arrived.
Unfortunately, the Safariland 6354DO will not work out of the box with OST-TSD modified slides that have iron sights in line with the Trijicon RMRs. It will only work with RMR mounted in the rear sight dove tail mount. I think this is a major oversight on the part of Safariland. Having the iron sights in line with the dot is what makes it practical as a carry/duty gun in the event the dot loses power or is broken. The OST-TSD configured slides are also the most common as they offer both off the shelf ready to go slides and machining services for your Glock factory slides. I would think that among serious users this configuration would be a lot more common than just dropping the dove tail mount in the rear of the slide.
Aside from those reasons, not making it work out of the box with the OST-TSD configured slide makes even less sense considering how minute the difference is to make it work. I was able to modify the holster to work with my OST-TSD Glock 34 in about 10 minutes, this included determining what I needed to change on the holster.
In this picture below you can see that the retention mechanism sits back about 1/8″ too far to allow the OST-TSD slide to sit all the way into the holster:
I used a belt sander to remove about 1/8″ of material from the top of the retention device and cleaned up the edges with a razor blade.
I used a heat gun for about 20 seconds on the front of the holster to reshape it so the RMR could drop all the way in
If you’re used to using the ALS holster and want commonality of training, or your department/agency requires the ALS mechanism you can make the 6354DO work with your OST-TSD slide.
If you want something that works out of the box with your OST-TSD slide, your best option is to buy the Bladetech unit that OST is selling.