Quote from xflat2186:
The overnight margin especially for a retail guy is silly on naked index puts. You're taking someone elses geopolitical risk each night for small premiums. The other issue is volatility skew in the puts is so great that in order to take in any decent premium on a spread you have to spread the strikes so far its hardly worth it. yes the volatility skew in the call side keeps premiums low but there is far far far less risk. Dont forget that many of the calls on barely move at all and surely underpeform their calculated delta on up moves since volatility falls.
ES options use SPAN margining which is much more generous than Reg T for option sellers. Portfolio margin is also better than Reg T but you need more then $100k.