[mkgmap-dev] Displaying highway shields on custom highway symbology

Greetings list. I have added code to my style file to display highway shields on highways, as is customary on maps in the United States. This works fine as long as I use the default mkgmap symbology. I tried substituting some custom linetypes for my highways, using a TYP file, and the shields disappeared. Do the shields only work with the default symbology? Mark Bradley