I already have 2 barrels and muzzle devices. I got tired of waiting for the rail that has been out of stock for the longest time with no signs when it will be back. Emailed the company and was politely answered that they don’t know when it will be back. I am now considering the KAC URX II.
They should work with your barrel options. The 10.5 will be mostly covered up by the URX II and and I am not sure if the KX3 will fit inside or that you wil be able to tighten it down.
Also remember, that no GB will fit inside the URX II. So either the GB or rail will have to be modified (unless you can get your hands on one of the special URX II’s that KAC modified).
You also realize that you need a special wrench for the install right?
There are a few dealers that install the rail for free if you purchase it from them, which eliminates concern for tool costs. I’m not sure which other rails you are looking at, but the URX II is certainly one of the top rails available.