It's about time someone look at Customer Portfolio Margin in light of its true advantage, "the offsets across product groups".
Most of the talk so far has been about the reduced margin requirements. Accounts setting at 17 or 18 percent requirement. The fact is that the equity percent that you are comfortable with under Reg T should be the one you use under CPM. The real advantage to CPM is the ability to use securities/options in one security class to hedge a position in another security class. Under Reg T a long position in SPY and short Calls in IWM would have the requirement on the long SPY side and the requirement on the naked calls. Under CPM the requirement on the SPY (Group 9) are offset @ 50% from the calls on IWM (Group 45).
Not knowing your strategy or the strike prices you are looking at I can't say. But the opportunity to put on complex security/options strategies within product groups and across security class to take advantage of higher premiums or temporary discrepancies in price movement of various indices is what CPM is all about.