RE: anyone have 41/37 spurs on the RS4?
I ran that setup with my RS4-3 a while back. I just Dremeled the slots in the chassis a bit to get the mesh right. Pay close attention to the second gear spur mesh with this gearing though. If the mesh wasn't perfect the second gear spur would strip out as soon as it engaged. You can also get away with a 17/23 pinion and 43/37 combo. I ran like this for a while also but it eventually took it's toll on the clutch finger. The acceleration was awsome though!