Hanzou
Grandmaster
Well it's not at all dissimilar to a number of ma, but anyway a fairly advanced level of yoga, gives you Extreme strengh, so it will with our doubt help at self defence.
So big guys don't need ma, but scrawny guys do, wouldnt that suggest that scrawny guys may just as well spend their time becoming big guys
Some scrawny guys can't become big guys due to genetics. There's nothing wrong with weight and endurance training though, even if you don't gain significant size.