No sophomore slump for Andreas Melbostad at Diesel Black Gold today. The energy level was high inside Grand Central's Vanderbilt Hall, and the clothes had a cool factor that's registering. Back in February, Melbostad established a structured, body-con look. Denim and leather remain the building blocks of the label; that's not changing. But for Spring, the jeans have a more generous fit (slouchy at the hips, with deep rolled cuffs at the ankle and strategic fraying here and there), and Melbostad cut his leather motorcycle jackets in icy blue and baby pink. Nice developments, both. Melbostad liked the notion of a "courageous fragility," and he played the brand codes against more delicate pieces, like cotton eyelet dresses with handkerchief hems and camisoles cut from gauzy silk in grayed-out pastels. Picking up where Fall left off, he put grommets on the hems of miniskirts and the sleeves of a leather jacket, and, taking that look a step forward, he decorated fun little dresses with shiny mirrored disks in geometric patterns. These gave off just a whiff of a bohemian vibe, but not enough to scare away the tough-chic Black Gold customer.