There are many ways to work when "TYP-ing".
When I get my hands on a map that I want to modify this is my way to work:

- Open the "active" TYP file in the map folder with TYPViewer. (backups made of course)
- Open the map in Mapsource (BaseCamp is slow and has nothing that I need in this case)
- Find out the details that you are not satisfied with and try to find them in TYPViewer. Modify at your taste.
- Close Mapsource (if TYP file is used by Mapsource it can not be overwritten by TYPViewer)
- Save TYP file with same name.
- Open Mapsource and press ctrl-G TWICE to clear cache and look at the result, modify again and repeat cycle.

- When you feel that you have done the job, transfer one tile to your gps and see what shows there. Mapsource/BaseCamp is one thing, your gps another unfortunately..

And to not be too much OT ; I found that the polyline "BARRIER" (or VÄGBOM i swedish) is made in a silly way. It is made as a 32 px long polyline and when zooming out it disapears for me. Better to remove the bitmap attribute and make a "normal" polyline. Works for me.