Custom Map Making - Custom Symbols

Hello,

This question may be to technical, but I had created a map years ago using GPSmapedit, laying down points for buoys and rocks. I then created a .img file to upload this map to my garmin etrex, gpsmap 76 etc.using Mapsource. I am now trying to put it on a 67i which really had no issue. All I did was plug the Garmin into the computer and transfer over the img file to the root folder. The problem is the custom symbols do not show. They have reverted to what must be preprogrammed into the 67i. You can see in the image that the red and black buoys are flags (This is OK) My original map had just simple red & black dots and all of my rocks where supposed to be asterisks, but now they show up as obstruction symbols which makes the gos screen very cluttered. Is there any way I can get my custom symbols back to show on the 67i?