Quite a lot of this would be non-obvious even if the send images were not done a different way. Which they are. So it takes a moment to wrap your head around, sorry._panbg images are the backgrounds for pan controls in slider mode. Not drawn when its a knob. _knob_ images are the static (non-rotating) image of a knob, which Reaper expects you to want the code pointer drawn over. Probably what you thought the bg images were. a rotating pan image like the send knob has ...doesn't exist. Which I approve of, because re-rasterizing bitmaps is yukky. OK, so, all we have so far is the _knob_ image. On top of this is going to be composited the code pointer. You can change the length of this by hacking the 'apparent' size of the knob while actually using a different sized _knob_ image file. We used to do this is lot, as you've probably guessed its a pain. Its colour is changed using the first four coordinates of *.pan.color in WALTER. ...OR... ...if you provide a bitmap stack, the code pointer won't be drawn. Even if your bitmap stack includes all knob as well as the pointer, Reaper doesn't know that and will continue to draw the _knob_ image underneath it. So then you might want to blank that.