Draf- I have that same problem In south dakota. Yeah go figure that one out no one is here except for radio towers.
I set up two v-files one for east and west. Then I break down the scan list according to county(section), I place all state TGRP's along with counties in the same list. Makes for some crazy looking lists at times. I then can place all towers on the scanner, then when I cross my border(river) I load the new v-file and tada. In a few mins. up and running again.
Not sure how busy your area is. Just make sure you set one scan list with ALL Talk groups scanned including wildcards. The state is always adding something here. Makes a great way to log information too.
The Roam feature works great cruising around at 70 mph. I use it and it works for me. Test it out with different % HI and % LOW you will have to find that sweet spot
Hope this helps you out some. I know that scan list idea has eased some confusion for my co-pilot too.