Most heavy a/c i have flown are easier to land with full flaps as you will establish approach speed easier - close to MALW you need every drag you can get. Another point is the line of sight, but I guess all those who need not see the TDZ are well of with lower flap settings.
On the other hand, instead of dumping 20000 gallons, consider an overweight landing, and you will need lower flaps (3/25/30/etc.) and a long rwy.
