Although I am one who definitely is in favor of aggressive attack on male pattern baldness, from the literature I have read, applying more than 1ml of minoxidil to your scalp will do no good.
From what I read, if you were applying 1ml to just one part of your scalp was somewhat wasteful, as there is a limit to the dosage/results ratio that stimulates hair growth. Spreading it out over front and vertex will put your usage of minoxidil more in line with what it was designed for. And besides, the chemical applied in one place does spread its effects to the entire scalp via the horney layer as evidenced by my thicker beard and eyebrows since I started applying minoxidil to my front and vertex.
Unless you are socretesian bald and only have a horseshoe of hair, I very much think that 1ml is fine for you.