Did you ever find a solution to this? I have a feeling I'm missing something simple, but I as well am getting about 100bps on file transfers. Considering it's been years since I last used Zmodem, I can't remember where to start troubleshooting a 1200 baud connection speed transfer over a 115k connection :-)

--- Update ---
Oops, forgot about the amazing differences in ASCII and Binary mode. The terminal program I had downloaded didn't have that option, and trying to use rz's option still didn't help. After getting binary mode on both sides, the file transfer flew.

Reg 1640, 6gb Blue empeg-car mark 1. SN 00359