It works for me :\
To change it to BigInt, you have to know JASS/vJASS
BigInt is essentially the core of all save/load. Save/Load itself is very tiny, most of it is BigInt =). It's just simple math. This means that you can modify any old save/load system to run on BigInt to generate the codes. It will, as a byproduct, be able to generate smaller codes and handle w/e ^)^.
There is also BitInt, which can handle even negative numbers.