First of all anavar is not for bulking.
The .2 mgs is just a rule of thumb that has been around since forever. The reasoning is that too little won't do anything and too much is just too expensive for the effects. On top of that it being a 17-alpha alkylated compound has some liver toxicity issues.
Another reason for the .2 mg. say you are a 200 pound guy. That means 40 mg per day. This makes 280 mg. per week.
Not that much compared to how some use test is it?
Oxandrolone is good for keeping gains while dieting and getting overall strength and hardness.
It is though a very expensive product.
At least that's what i have read.