>>316161678
To add to that even further, you'll want to replace the corresponding 1080p in all of the shader files of VRCLens with your custom res, to fix the ringing artefacts that you'll still get in your depth of field blur if you only fix the render textures. 

Or you can just wait for the creator to fix it. I've contacted them, and they said they're already working on a new update again.