First thing I'd suggest is making sure you give VPC enough memory. I run on a Quicksilver 866 to a Legend (but with OS9.2.2) and found some help by doing that. I added 10,000 k to mine.
Also, choke back the baud rate, mine seems to be more reliable at 9600. It takes 30 minutes to fill my Legend, but it works. Faster would be better, but I'll go with what works everytime.