Next to composing a personal "universe" of ETF's (defaults are EFA, IWM, SPY and TLT), the script furthermore allows to adjust the length and smoothing inputs for the ROC calculations (defaults: 60,5) to simplify backtesting. When for instance SPY is exchanged for VWO, the highest NLV is achieved with (60,1). The 60 days setting seems quite optimal though, just like Kevin McGrath's backtesting showed. Remember to adjust settings both for TAA_Rotation and for TAA_Equity.
A more aggressive approach would be selecting four triple leveraged ETF's: DZK, TNA, EDC and TMF (the 300% versions of the default universe). This combo may generate huge gains but be prepared for horrific drawbacks too (see chart below with in this case a 3 year time span because Direxion introduced TMF in April 2009). BTW, using inverse ETF's like SH seems not to improve profitability.
Please share your comment's and idea's for improvement.
Do your own due diligence, trade safe and enjoy!
[Update March 10, 2013: nested "concat" statements added in TAA_Equity script]