Hi, Ken:
Leave the handheld GPS topside, if that's your practice. You can get a
GPS with a USB cable for as little as $36.95. Just plug it right into your laptop.
This GPS works just fine inside the cabin on our boat, and its performance is amazing compared to older generation devices.
When you're tiptoeing into that creek with the winding, unmarked channel, just bring the laptop and GPS up on deck, and drill down in the electronic charts on the laptop.
I love both of the programs you mentioned.
Bill