Reducing the length of the cahin should help.
If you have them all linked in a continuous line, the first segment get hammered with traffic. For example, I'll use fake 10 port switches. The first switch has 9 computers on it and 1 link to the next switch. Do this for each switch succsively. You now have 2 switches x 9 computer/switch (2nd & 3rd switch) + 10 computers on the 4th (last) switch = 28 computers all pushing data across that 1st link between switch 1 & 2.
Now if you were to hang 3 of the switches off the 1st switch, each lan segment between the first switch and the next switch only has to handle 10 computers each. You can do the math for other arrangements.
Anyhow, hope that helps.