All protocols allow for some variation in packet sizes, timeouts, and the like. Usually, the defaults provided work well under standard circumstances, but may not be optimal for your situation. The g protocol, for instance, uses window sizes from 1 to 7, and packet sizes in powers of 2 ranging from 64 through 4096. If your telephone line is usually so noisy that it drops more than 5 percent all packets, you should probably lower the packet size and shrink the window. On the other hand, on very good telephone lines the protocol overhead of sending ACKs for every 128 bytes may prove wasteful, so that you might increase the packet size to 512 or even 1024.
Taylor UUCP provides a meachanism to suit your needs by tuning these parameters with the protocol-parameter command in the sys file. For instance, to set the g protocol's packet size to 512 when talking to pablo, you have to add:
system pablo ... protocol-parameter g packet-size 512
The tunable parameters and their names vary from protocol to protocol. For a complete list of them please refer to the documentation enclosed in the Taylor UUCP source.