I have a bene 473, if I really eek it out, I'll get less than 3 l/hr at 5 kts, providing it not pushing into wind, seas. You'll have wind/seas astern, so that will help.
Previous owner did 4 Atlantic crossings, 2 each way, boat has a 237 litre tank, and 4 x 20 litre jerry cans. No genset, he managed with plenty to spare, also at the time, boat had no wind or solar
means of battery charging
The 4 jerry cans I have live in the stbd lazerette.