I tried again to create images brushes with AP, but the default size of 64 pixels for new brushes is turning this into a very annoying experience. If I draw a 24 x 50 pixels or 200 x 150 pixels large object for export as brush, then it should stay this size and not blown up or shrink. Apart from the size issue the new brush becomes blurry when it is increased to the current default size. The fact that I can change the brush size afterwards is no help.
The current solution is good for simple shapes but not for the creation of more sophisticated brushes. At least it would help if the user could choose between a fixed brush size or the original size.
This may not be a problem for most users but for artists who need a lot of brushes for their work it is a serious matter.