It's been ages since I've used a serial modem! But I remember I had to use a different serial.device to get higher speeds. I believe this was on the old A500, but may have carried over to the A1200 too.
Obviously the names of the newer files were NOT "serial.device" - but I can't remember what they were.
Edit: 8n1.lha is one of the files, and New8n1.lha Hope this helps...
