Setting a static number (300, 600, etc) won't be of any benefit. What causes "lag" is not necessarily a high ping, but an unstable ping. I.e. one that jumps from 100 to 500 in the space of a few milliseconds. If your ping is high but stable, chances are there will be not be any major issues.
At best, setting ping limits would be a poor band-aid -- not a solution.
SA:MP is very poorly designed and there isn't really a good solution. We just have to make the best of a shitty situation and hope that "laggers" are few and far between.