This is been debated before and I think it's agreed that most manufacturers err on the cautious side with respect to overcoating times. When time or weather has dictated I have put on a second coat of Blakes Tiger within 2-3 hours and that was in March when the temperature was lower. I've also found the same applies to International and XM products so I imagine Plastimo would be similar.
Also look at recommended drying times before immersion but many people manage to antifoul successfully between tides.