I have thought long and hard about momentum strategies on individual stocks and posted my own system on another thread.
In my view the only real difficulties are portfolio choice and the use of a filter.
Portfolio choice HAS to be generalised by reference to market cap or volume or some fundamental factor and not by reference to individual named stocks
Any backtest HAS to include delisted stocks.
Filter is slightly more difficult. You will see that my system does not use a filter. The reason is a fear of curve fitting but that fear may be misjudged.
Don't go long if S&P 500 or some other index is negative. Probably needs to be done but it makes me a bit nervous. I'm less nervous having just done a 116 year test on the Dow and the S &P but of course no backtest has any real predictive power.