Beags - a serial DCC at the maximal 115200 baud (COM port with a FIFO-buffering 16550A) works out at a theoretical 9-10Kb/sec or about 36Mb/hr, so 16 hours for 350Mb of data sounds about right. Yawn....glad it worked anyway.
Using the parallel printer port for the DCC-connection allows a much higher transfer rate, with a Basic 4 bit "LapLink type" should be around 60-80 Kb/sec. With a "DirectParallelŽ Universal Fast Cable" supposedly 300-600 Kb/sec. An Ethernet 10 MBit connection through-put is approx. 300 Kb/sec, so 30-150 times faster than a serial connection.