Haven't read Margin of Safety (Pretty rare by the look of it) but do have Greenblatts Little Book from back in the day when I considered myself an investor. Now as a speculator the method doesn't have the risk control I desire.
well, from a speculators standpoint, you need to pay attention to your factor risk, risk budget (var), and other metrics. Stop losses aren't effective tools because you when you really need it, it doesn't work as well; and if your investment framework is just momentum, it is hard for you to come up with an expected return framework to compare vs. ex-ante risk.
This is where (a) sources of return, (b) sources of alpha, and (c) sources of risk need to come together. For example, if you are seeking to invest in XYZ security because (a) company is expanding production (b)
faster than expected you can distill this into a price and generate an expectation of returns.
Sources of risk include factors (how sensitive is the stock to market, to interest rates, etc.), its own historical volatility (how much does it fluctuate on average), and liquidity (how much will it cost you to enter or exit the trade?) + others/idiosyncratic issues.
So if the stock is trading at $25 expected EPS growth of 15% and your view is that EPS growth will be 20%, then you think the stock is actually worth $33.2 which is a 32% expected return.
If the stock fluctuates on average by 20% each year, then you can expect the stock go move up/down $5 from 25 (even if you are wrong the stock can still go up to $30). You will know whether you are right or wrong when the company reports earnings and those higher production numbers will be printed.
So now you have two risk items you can use -- 1) you should expect the stock to not go down past $5/252 * days to earnings, 2) you will know whether your thesis is right/wrong once earnings are announced.
Now you can set risk limits to trim/add to position when risk limits are breached. You can do so either cyclically or counter cyclically depending on your conviction.