I haven't used any DBU for awhile and never tried it with SPI intercoat but I'd bet you won't have any problems. I'd do like Crash suggests- shoot two coats of black over the stripe areas, skip the intercoat, let the black cure up for 4hrs-(no sense in rushing it), then tape off your stripes, tack rag it, shoot your white and let it flash off good, unmask, tack rag it, then clear it. You'll end up with a much cleaner job this way and it's easier masking.