I've been trying to use:
--icarus-timing short
instead of:
--icarus-timing 3.0=100

It seems to be giving me a little more speed: about 335 MH/s instead of 334 MH/s

These options are explained in the file FPGA-README in cgminer source code.
The "short" options basically finds the timing by calculating it and periodically adjusting it in the first hour it runs. You will see a message in the log about these adjustments every once in a while if you try it.
The "3.0=100" is probably a safe timing that works fine for every unit. The thing is that all sticks are not exactly the same and some units might be able to cope with a slightly better timing value.