I/O Buffer settings?

I'm using Smart FTPv1.0.979, I have a cable modem connection. My uploads seem to max at 16-20KB according to the Transfer window. This seems very slow considering the connection. I've seen ppl on the board mention "increasing the I/O buffer" and have it work fine. How do I do that?

+- System -----------------------------

Microsoft Windows XP Home
Service Pack 1 (Build 2600)

CPU Speed : 1202 MHz
Total Memory : 391716 KB
Free Memory : 62540 KB

+- SmartFTP ---------------------------

Version : 1.0.979.4
Time Stamp : 2003-10-19 17:59:43

+- Application DLL --------------------

controls.dll : 1.6.979.4
ftpapi.dll : 2.0.979.4
language.dll : 1.0.979.4
reseng.dll : 1.3.979.4
smarthook.dll : 1.0.2.1

+- System DLL -------------------------

shell32.dll : 6.00.2800.1233 (xpsp2.030604-1804)
shlwapi.dll : 6.00.2800.1226
comctl32.dll : 6.0 (xpsp1.020828-1920)
riched20.dll : 5.30.23.1211
schannel.dll : 5.1.2600.1106 (xpsp1.020828-1920)

+- Internet Explorer ------------------

Version : 6.0.2800.1106

+- Winsock ----------------------------

Winsock : 2.2

At this moment it's hardcoded, you can't change it with that hardcoded settings my uploads over a 100 mbps lan goes up to 9 MB/s