ST6 are not valiable in playermodel list, so follow this instruction how to get ST6 playermodel

1. Spawn a category of St6 playermodel ragdoll. The playermodel one is tagged with "pm" text, or not (go to your spawnlist, addon, and find CSGO, click it and search for your ST6 variant. Be careful! sometimes you get wrong to spawn the ragdoll, maybe you will spawn the npc one. The npc is tagged with "npc" text)

2. Use model manipulator mod
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=105920435&searchtext=model+manipulator
and use your toolgun and search for model manipulator tool category

3. Point it into the ragdoll with your toolgun, then, when you already point your toolgun into the ragdoll, right click on the ragdoll with the mouse button selected. Thats how you can get your model you know

4. You did great! Now, press R on your keyboard to set it as your playermodel

5. You have your own ST6 PM. You're doing fantastic...