Having used a few of these, it’s overrated. I’d just use wide black colored duct tape and tape up the whole unused port. On top of that, if your screws ever loosen it’ll jam up the intervals. Secondly those tapered screws once were stuck and the small Allen key slot stripped, needing to be drilled out to disassemble.
For QD you might want to use an Magpul RSA instead mounted directly on the top rail, works very well.