I'm attempting to create a custom marker from a path. I've attached a file that illustrates what I'm attempting. In the file there are three paths: a bezier curve and 2 identical arrows. When I make one of these paths into a marker with Object>Objects to marker and then select it in stroke style from the bezier curve, the marker that appears at the end of the curve is larger than the original path. How can I have these be the same size? I've also attached an image to illustrate the issue. I believe the issue has something to do with the stroke width of the original path arrow. However, I don't want to use a stroke width of 2px when creating it (the same as the bezier curve), because I don't know how to get it to the exact right shape and size with that method.

You need to use absolute units if you want the market to maintain the same size for all stroke widths.