Rogaine on hairline AND scalp?

[RickonLives]

I'm in my early 20s, about to try Rogaine for the first time, and I had a question for someone here who might be more in the know about how the product works.

I'm dealing with a receding hairline and a thin patch on my scalp, so I'd ideally like to apply Rogaine to both, even though the product only advertises the scalp. What I'm wondering is will this require two doses, half a cap on my scalp, half a cap for my hairline? I'd really like to address both but going through Rogaine at twice the recommended pace is really going to hit the wallet of someone making early 20s money, to I wanted to check. Thanks!