Finding ETF-s and mutual funds with a long history might be a challenge. It's advised to use alternatives which should generally provide same results. I found that vanguard's index mutual funds are a good replacement for ETF-s when I want to test a period beyond 10 years.
* Instead of SPY, I change the portfolio to invest in VFINX
* Instead of SHY/AGG etc, I change the portfolio to invest in VBISX
Now testing with a bull/bear strategy simulator - I get the following stunning result:
Could investing be this simple? Follow one simple signal and alternate between bull and bear portfolio? Try for your self - download the software and experiment with your desired allocations.