I just bought a couple of Verbatim 16 DVD+R spindles. To my surprise, they burn only at 2.4x and 4x on a NEC 2510. This is a 8x burner. Burning Verbatims 8x (or Fuji's) DVD+R's have an expected 8x speed. Is this 4x speed, because the 16x DVD's have a limited 'speed-spectre' ?