Lyntris' shares fell 11.4% in the defense contractor's New York debut on Wednesday, giving the company a valuation of $1.78 billion and underscoring investor caution toward new listings. Shares opened at $15.5 each, below the initial public offering price of $17.50 apiece. The Falls Church, Virginia-based company and some existing shareholders downsized the IPO to 17 million shares on Tuesday and raised $297.5 million, after initially marketing 24 million shares at $19 to $22 apiece. The company sold about 5.7 million shares in the IPO, more than its earlier proposal of about 4.9 million shares, while existing shareholders cut their offering by more than 7.8 million shares. The U.S. IPO market has rebounded strongly in recent months, but investors remain selective, forcing several companies to trim their deal sizes.