I have noticed the same problems. I found out that the lake i go to gets drained quite a bit and it is a shallow lake. maybe that could be some of the probem. I have been to the point of actuall confusion. I go out to the lake with no wieght at all and get the same size wake as 400lbs of sand in the front ....ballast of 500lbs in the back 600 lbs of granite in the back and 2 fat sacks of about 200 lbs each on the sides and notice no difference....WHAT GIVES?? Just the lake stickin' it to us i guess.