It's super important to buy companies you understand. I have a...

It's super important to buy companies you understand.
I have a small concentrated portfolio and have had 20% per annum compounding for the last 4 years, not beating the market by that much. It's been a raging bull market but now is time for extreme caution I think.
There are only few companies I can understand well and determine are "bargain issues" selling below 50% of what they are worth.
I have a few MMA but am still researching/watching for results. A value analyst would look at it and say the 10 year history is good but probably not representative of the future - particularly the large LNG projects. The balance sheet is O.K.
Mainly though it has been slammed by oil prices, if it can generate cashflow in this environment to pay debt then it becomes a very safe investment in my view. Over the long term the oil industry will recover.
In fact the oil companies are going to rue the day that they forced MMA to sell it's anchor handling tugs to cart rocks around.
Graham would want an EBIT/fixed charges coverage of more than 3 before investing.