Rage3D have updated their tweak tool again. Here's what's new:

Added Force Pixel Shader Version for DirectX Added Force Vertex Shader Version for DirectX Note: You cannot force a higher shader version than your hardware actually supports. These tweaks are for forcing lower shader versions than your card supports. ex: There is no way that PS 2.0 will work on your Radeon DDR, I'm sorry. 3.8b update: Added support for R350 based cards, others to come soon 3.8b update: Completely rewritten overclocking libraries

Download Rage3D Tweak v3.8b