IMO you should mention this on http://zorro-trader.com/manual/en/optimize.htm

Also, why does the script stop when it hits this limit? Can't it just move on using the first 256 steps and just log a warning instead of an error?

Also also
I find myself pulling out a calculator to figure out how many steps there will be, especially when using the fractional increment feature.
What about yet another signature for optimize. When the fourth argument is zero, it automatically figures out the the right ratio to make 20 steps since 20 is a nice number.
optimize(1, 1, 10, 0) --> [1, 1.122, 1.259, 1.412, 1.585, 1.778, 1.995,2.238, 2.512, 2.818, 3.162, 3.547, 3.980, 4.466, 5.011, 5.622, 6.308, 7.077, 7.941, 8.910, 9.997]
(corresponding to a fourth term of 1.122)

It will be mentioned. Step size 0 already means a 10% increase per step, so the number of steps would require an additional parameter.