I guess it depends what you are doing with it. If you spend the whole day pootering about at idle to fish or rescue sailing dinghies, you could get away with a lighter mix.
Bear in mind some of the auto oilers run something like 200:1 at idle!
I will having said that agree with above -if you are running flat out most of the time, 50:1 won't do it any harm.
For what it's worth, when pre- oiling a tank, the thing to remember is that for 50:1, 2% of your tank volume should be oil, so for a
30L tank, you need 600 mL of oil
25L tank, you need 500 mL of oil
22L tank, you need 440 mL of oil
5L tank, you need 100 mL of oil
The down side to this is that you can't use a standard Cola bottle to "pre charge" a 30L tank...