I gave up on DXF codes with MLEADERs and went the VLA Route.
Here is my routine to convert qleaders to mleaders, you will need to make modifications for your standards. The lines that need to be changed should all be commented. This should give you a good starting point. This is one portion of our routines for working with leaders, I do have many more, but it should give an idea of how to work with leaders. Please note that I did not originally create this routine, I have only made changes to it, to improve upon what was already there. Please let me know if you have any questions about it.
Edit: Found a slight bug, code has been updated.
