Clive, I am still interested in AIMing SSO as it is simpler than other methods.
Here are two quick tests I just performed: 67% cash (VFISX), 67% sell Vealie, 20% buy SAFE, 0% sell SAFE, 10% MTS, reviewed quarterly. Less frequent reviews are key.
In the first test (upper chart), we start from June 2006 (as far back as SSO history goes). MaxDD was 19% and cash got as low as 36%, hence equity leverage would've been 2*(1-0.36) = ~1.3 at most.
In the second test (lower chart), we start from Sep 2007 (close to market top on a quarterly basis). MaxDD was ~35% and cash got as low as 25%, hence an equity leverage of 2*(1-0.25) = ~1.5.
I think based on the above results, perhaps one can use a portion of cash in long term bonds in order e to boost returns. So rather than using 67% in callable cash, one can use 20% in long term bonds, 47% in VFISX and 33% in SSO. If higher yield / longer term bond can add 2%, then this would roughly add 0.4% overall.
I think overall, this compares quite well with your testing of the method that uses higher yielding bonds for the fixed income portion, and (AIM-able) virtual cash with SPY and SSO for the equity portion, but for slightly higher risk.