optimal TCP/IP registry setttings for FR

Our branch offices are connected to Corporate office via Frame Relay 128K or 64K line. In our branch offices, there are Win9x clients that access NT servers at Corporate office.

Any one knows what is the optimal registry TCP/IP settings (DefaultRcvWindow,MaxConnectRetries, MaxDataRetries, MaxMTU…etc) for FR 128K or 64K connections?

Note:
10% of frames are less than 64 bytes
45% of frames are between 65 to 127 bytes
25% of frames are between 128 to 255 bytes
8% of frames are between 256 to 511 bytes
4% of frames are between 512 to 1023 bytes
8% of frames are between 1024 to 1518 bytes

Appreciate the help!