Garmin GNS 430/530 User Waypoints

Hello,
I am investigating about uploading from a PC and through the serial
interface some hundreds of User Waypoints, necessary for VFR flight into
a GNS 430.

It seems that it is not officially feasible due to certification
issues. That seems stupid, while manually entering waypoints may be
worst that through a PC and a verified database, anyway, that is what
garmin sais.

Anyway, the function "crossfill" is available when two similar
units are connected through the #3 serial port (RS232), just to send
[all] the waypoints between the units. This seems a beautiful way to
send them from a PC, simulating we are a GPS! In addition, on the user
guide, it is also mentioned that user waypoints can be sent by an EFIS
with Joystick, but once again, nothing more is reported about the
protocol used.

I could write the program, but I would like to know if someone else
before faced the problem and discovered more informations about the
protocol used.

Thanks.

Giuliano Rescaldani