There are no rules in the current IM as long as you stick within the confines of the simulator code (meaning you introduce whatever bots you want, run whatever physicis or costs you want, run as many different machiens as you want, etc. but if you start writing your own code to talk to the FTP server directly to spam or cheat the the system, I am going to have words with you).
There are many things that influence performance and there are detailed posts of the subject but bot proximity is perhaps the second biggest factor (after total number of bots). Non-intuitivly, running a larger field size, all else being equal, will speed up your sim considerably as it allows the code to ignore cases where bots are too far away to see each other, etc.