I would like to peacefully disagree

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It should work if you can configure your GPS to output standard NMEA data, instead of the Garmin binary format. The specs for the unit at the Garmin website indicate that it can output both formats.
You may also have to install port splitter software (do a search for xport). This allows you to split the data from one hardware port into several virtual ports in order to feed data to several programs at the same time. I had a Garmin running through both a serial port and a serial-to-USB adapter working fine in several different programs before I got a USB powered device.
Good luck..