The phrase "allowed not only" is correct and usable in written English.
You can use this phrase when you want to indicate that something can be done in multiple ways. For example: "The teacher allowed not only written assignments but also verbal presentations for the class project."
He has been allowed not only to live in what one US official called a "studio" in Camp Echo.
Employees were allowed not only to choose how to fulfil their orders, but also to trade on their own account.
We're human, and we're allowed not only to be flawed, but also to be bummed out by those flaws on occasion.
And in pursuing a Firrea lawsuit, prosecutors are allowed not only to issue subpoenas, but also to take the sworn testimony of individuals.
His letter called Mr. Troy "a radically and pervasively disturbed person," adding, "I cannot fathom why he was allowed not only to stand trial as sane, but more especially to be permitted to defend himself".
But if we are in a jug it is transparent, not opaque, and one is allowed not only to see outside but to read what is going on out there; to make identifications as to values and human quality.
And a narrative structure was adopted that allows not only for extended but for infinite treatment.
Better still, as this book shows, they allow not only birds but the human imagination to take flight.
Israel's "law of return" allows not only Jews but their partners, children and grandchildren, who may not be technically Jewish, to claim Israeli citizenship.
The Opus connects to the Internet, allowing not only for online radio, but giving users remote control once its included software is installed on a touch-screen P.D.A.
This allows not only state institutions but also individuals to make complaints that then must at least be considered by the judicial authorities.
