Problem with LLC converter design

I have been attempting to design an LLC resonant converter using guidelines on application notes and other literature. However, the resonant inductor values I get are way too small (275nH) and I'm not sure how do-able this is. I have attached the design guide I used. I'd like to get recommendations or perhaps other design guides that would suit my application. My specs are as follows Vin = 24V, Vout = 350V, Po = 1KW. I chose an inductor ratio of 6, n = 12 and resonant frequency at 150Khz.