I thought that this kayak was trimmed a little too far aft, that is, that the bow was a little higher than necessary. I originally tried to velcro the bottle & boat together, but it doesn't hold on the water. I got an inexpensive hold-down strap, and glued it down with a blob of epoxy. I orginally tried a full gallon of water, but it was excessive-1/2 gallon seems about right. I think it helps, but I'm still experimenting.