For those in a position to bump up against those limits, it's easy. :)
Speculative position limits:
S&P 500 ... 20,000 contracts
E-mini S&P 500 ... 100,000
OR any equivalent combination of the two, e.g., 10,000 full + 50,000 E-mini
Reporting levels:
S&P 500 ... 1,000
E-mini S&P...